Summary of the invention
Technical problem: the object of this invention is to provide the two clamped beam switch double grid HEMT frequency multiplier of a kind of GaAs base low-leakage current, two grids are positioned at immediately below two clamped beam switches, reference signal and reference signal are carried on two clamped beam switches respectively, the conducting of clamped beam switch control HEMT in circuit, by to the control of two clamped beam switches and the effect of external circuits, realize the computing to reference signal frequency, obtain target frequency.
Technical scheme: the HEMT of the two clamped beam switch double grid frequency multiplier of GaAs based low-leakage current of the present invention is growth enhancement mode HEMT on gaas substrates, comprises intrinsic GaAs layer, intrinsic AlGaAs layer, N+AlGaAs layer, source electrode, drain electrode, grid, anchor district, clamped beam switch, drop-down pole plate, insulating barrier, through hole, lead-in wire, there is intrinsic GaAs layer on gaas substrates, intrinsic GaAs layer there is intrinsic AlGaAs layer, intrinsic AlGaAs layer there is N+AlGaAs layer, source electrode, drain electrode is positioned at the both sides of two clamped beam switches, source ground, two grids are set up in parallel, with two clamped beam switch one_to_one corresponding, the two ends of clamped beam switch are fixed in anchor district, the middle part of clamped beam switch is suspended on grid, drop-down pole plate is arranged between anchor district and grid, drop-down pole plate ground connection, insulating barrier covers on drop-down pole plate, direct current biasing acts on clamped beam switch by high frequency choke coil and anchor district, the actuation voltage of clamped beam switch is designed to the threshold voltage of HEMT, lead-in wire connects intrinsic GaAs layer respectively by through hole,
HEMT drain electrode output signal has two kinds of different working methods, one is that selection first port inputs to low pass filter, low pass filter exports access voltage controlled oscillator, voltage controlled oscillator exports by the 3rd port access divider, divider output signal is loaded on a clamped beam switch as feedback signal by anchor district, form feedback loop, reference signal is loaded on another clamped beam switch by anchor district, and the another kind of working method of HEMT drain electrode output signal is that selection second port directly exports amplifying signal.
Closed or the disconnection of clamped beam switch is controlled by direct current biasing, when two clamped beam switches all realize drop-down under the direct current biasing reaching or surpassing actuation voltage, with gate contact, when switch closes, under the effect of gate voltage, form Two-dimensional electron gas channel, HEMT conducting, reference signal realizes being multiplied by HEMT with feedback signal, drain electrode output packet is containing the phase information of two signals, select the first port input low pass filter, filtering HFS, output packet is containing the direct voltage of phase information, direct voltage inputs voltage controlled oscillator as control voltage, the output frequency of voltage controlled oscillator is conditioned, signal after regulating frequency through the 3rd port transmission to divider, divider output signal is loaded on clamped beam switch as feedback signal, the result of looped cycle feedback is that feedback signal is equal with the frequency of reference signal, voltage controlled oscillator the 4th port output frequency f
ofor N times: the N × f of reference signal frequency
ref, realize the frequency multiplication of reference signal,
When direct current biasing is less than actuation voltage, two clamped beam switches all not with gate contact, when switch disconnects, gate voltage is 0, HEMT cut-off, effectively can reduce grid leakage current, reduces power consumption;
Close when only having a clamped beam switch, when another clamped beam switch is in off-state, Two-dimensional electron gas channel is formed below closed clamped beam switch, high resistance area is formed below the clamped beam switch disconnected, the structure that raceway groove is connected with high resistance area is conducive to the reverse breakdown voltage improving HEMT, only have the gating signal on closed clamped beam switch can be amplified by HEMT, amplifying signal exports through the second port, when only having the clamped beam switch loading reference signal to close, reference signal is amplified by HEMT, and the second port exports reference signal frequency f
refamplifying signal, when only have load the clamped beam switch of feedback signal close time, feedback signal is amplified by HEMT, and feedback frequency signal is voltage controlled oscillator output frequency f
odivided by the result of N: f after divider
o/ N, the second port output frequency is f
othe amplifying signal of/N, the clamped beam switch of disconnection is also conducive to reducing grid leakage current, reduces power consumption.
Beneficial effect: the two clamped beam switch double grid HEMT frequency multiplier of GaAs base low-leakage current of the present invention has following significant advantage:
1, two clamped beam switches play the effect of switch in circuit, the conducting of convenient control HEMT.
2, that circuit is facilitated is controlled for clamped beam construction of switch, by the control to single clamped beam switch, realizes to the process of individual signals, making Multifunctional circuit, expanded application scope.
3, HEMT combines with MEMS technology, circuit efficiency is promoted, lower power consumption, simplifies the structure, and volume is miniaturized.
Embodiment
The two clamped beam switch double grid HEMT frequency multiplier of GaAs base low-leakage current of the present invention comprises GaAs substrate, enhancement mode HEMT, and external low pass filter, voltage controlled oscillator, divider, high frequency choke coil; Wherein HEMT growth on gaas substrates, is followed successively by intrinsic GaAs layer from bottom to up, intrinsic AlGaAs layer, N+AlGaAs layer, and two grids arranged side by side are positioned on N+AlGaAs layer; Source electrode and drain electrode are deep into intrinsic GaAs layer in addition.Intrinsic GaAs layer and intrinsic AlGaAs layer form heterojunction, and grid and N+AlGAs form Schottky contacts.Two clamped beam switches are suspended in directly over two grids respectively by anchor district.Be provided with drop-down pole plate between grid and anchor district, drop-down pole plate ground connection, insulating barrier covers on drop-down pole plate.
Reference signal and feedback signal are loaded on two clamped beam switches respectively by anchor district.Direct current biasing is acted on clamped beam switch by high frequency choke coil and anchor district.High frequency choke coil ensures that direct current biasing and AC signal separate.
The actuation voltage of clamped beam switch is designed to the threshold voltage of HEMT.When direct current biasing is less than actuation voltage, two clamped beam switches are all in suspend and disconnect, time not with gate contact, grid voltage is 0, for enhancement mode HEMT, Schottky barrier is deep into intrinsic GaAs layer, and the two-dimensional electron gas on intrinsic GaAs layer and intrinsic AlGaAs layer heterojunction border is depleted, so HEMT cannot conducting.
Reach when direct current biasing or be greater than actuation voltage, two clamped beam switches all drop-down closed with gate contact time, gate voltage is the size of direct current biasing, now Schottky barrier narrows, two-dimensional electron gas increases, and HEMT conducting, reference signal is multiplied by HEMT with feedback signal.Drain electrode outputs signal the phase information contained between reference signal and feedback signal.Low pass filter by the high fdrequency component filtering in this signal, and carries a direct voltage to voltage controlled oscillator, regulates the frequency of the output signal of voltage controlled oscillator.Voltage controlled oscillator output signal is after divider, the corresponding change that 1/N occurs in frequency, and as feedback signal, re-enter HEMT, through the effect of loop, feedback signal and reference signal reach locking, and namely voltage controlled oscillator output frequency is equal with reference signal frequency divided by the frequency after N.So the signal frequency that final voltage controlled oscillator exports is N times of reference signal frequency, realizes frequency multiplication.
When only having a clamped beam switch to close with corresponding gate contact, Two-dimensional electron gas channel is formed below closed clamped beam switch, be high resistance area below another clamped beam disconnected, the structure that raceway groove is connected with high resistance area effectively can improve the reverse breakdown voltage of device.Only have the gating signal on corresponding clamped beam switch can be amplified by HEMT to export.Thus by the independent control to a clamped beam switch, realize the amplification to individual signals, expand the range of application of circuit.
Below in conjunction with accompanying drawing, the two clamped beam switch double grid HEMT frequency multiplier of GaAs base low-leakage current of the present invention is further explained.
As shown in Figure 1, the two clamped beam switch double grid HEMT frequency multiplier of GaAs base low-leakage current of the present invention comprises GaAs substrate 1, arranges enhancement mode HEMT on gaas substrates, external low pass filter, voltage controlled oscillator, divider, high frequency choke coil.
HEMT comprises intrinsic GaAs layer 2, intrinsic AlGaAs layer 3, N+AlGaAs layer 4, source electrode 5, and drain 6, two grids 7,8, two, anchor district clamped beam switch 9, drop-down pole plate 10, insulating barrier 11, through hole 12, lead-in wire 13.Wherein, source electrode 5 ground connection, clamped beam switch 9 is suspended in above grid 7 by anchor district 8, two grids 7 and two clamped beam switch 9 one_to_one corresponding, and drop-down pole plate 10 is arranged on below clamped beam switch 9, lower rubbish pole plate 10 ground connection.Inner in HEMT-structure, grid 7 and N+AlGaAs layer 4 form Schottky contacts, and intrinsic AlGaAs layer 3 and intrinsic GaAs layer 2 form heterojunction.For enhancement mode HEMT, when gate voltage is 0, the Two-dimensional electron gas channel of heterojunction boundary is exhausted by Schottky contacts.
HEMT drain electrode 6 output signal can select two kinds of working methods, one is that selection first port 14 accesses low pass filter, low pass filter exports access voltage controlled oscillator, voltage controlled oscillator exports and accesses divider by the 3rd port one 6, the output signal of divider accesses a clamped beam switch 9 as feedback signal by anchor district 8, and reference signal accesses another clamped beam switch by anchor district 8.The another kind of working method of HEMT drain electrode 6 output signal is that selection second port one 5 directly exports amplifying signal.
Direct current biasing is acted on clamped beam switch by high frequency choke coil and anchor district 8.High frequency choke coil ensures that direct current biasing and AC signal separate.The actuation voltage of clamped beam switch 9 is designed to the threshold voltage of HEMT, when direct current biasing is less than actuation voltage, clamped beam switch does not contact with grid 7, when switch disconnects, gate voltage is 0, and heterojunction boundary does not have Two-dimensional electron gas channel, and HEMT ends, effectively can reduce grid leakage current, reduce power consumption.
When direct current biasing reaches or surpasses actuation voltage, two clamped beam switches 9 are all drop-down to be contacted with grid 7, and when switch closes, under the effect of gate voltage, two-dimensional electron gas is assembled at heterojunction boundary, forms raceway groove, as shown in Figure 4, and HEMT conducting.Reference signal is multiplied by HEMT with feedback signal.Drain electrode 6 outputs signal the phase information contained between two signals, selects the first port 14 to input low pass filter, the high fdrequency component filtering during drain electrode exports by low pass filter, and carry a direct voltage to voltage controlled oscillator, direct voltage can be expressed as:
Wherein K is HEMT gain coefficient, f
reffor reference signal frequency, f
backfor feedback frequency signal, φ is that proper phase is poor.Voltage controlled oscillator under the control of direct voltage, the size of regulation output signal frequency.Voltage controlled oscillator output frequency can be expressed by following differential representation formula:
Wherein, f
ofor voltage controlled oscillator output frequency, K
vfor voltage controlled oscillator sensitivity.After divider, frequency becomes original 1/N, and as feedback signal, re-enters HEMT.Namely:
Through feedback ringing, the frequency final sum reference signal of feedback signal is consistent.That is:
So the signal frequency that final voltage controlled oscillator the 3rd port one 7 exports is N times of reference signal frequency, realizes the frequency multiplication of reference signal.
Only has a clamped beam switch 9 by drop-down closed, when another clamped beam switch 9 is in suspension off-state, Two-dimensional electron gas channel is formed below closed clamped beam switch 9, be high resistance area below the clamped beam switch 9 disconnected, as shown in Figure 5, raceway groove is connected with high resistance area, is conducive to improving reverse breakdown voltage.Now, only have the gating signal on closed clamped beam switch 9 can be amplified by HEMT, amplifying signal is exported by the second port one 5.When only having the clamped beam switch 9 loading reference signal to close, reference signal is amplified by HEMT, and the second port one 5 output frequency is f
refamplifying signal.When only having the clamped beam switch 9 loading feedback signal to close, feedback frequency signal is the result of pressuring controlling oscillator frequency after divider, i.e. f
o/ N, so the second port one 5 output frequency is f
othe amplifying signal of/N.Thus by the independent control to a clamped beam switch 9, realize the amplification to individual signals, expand the range of application of circuit.In addition, for the clamped beam switch 9 disconnected, can grid leakage current be reduced, reduce power consumption.
The preparation method of the two clamped beam switch double grid HEMT frequency multiplier of GaAs base low-leakage current of the present invention is as follows:
1) at semi-insulating P type GaAs substrate;
2) epitaxial growth intrinsic GaAs layer about 500nm;
3) epitaxial growth intrinsic AlGaAs separator is about 50nm;
4) grow N+ type AlGaAs layer about 20nm, doping content is 1 × 10
18cm
-3, control thickness and doping content, make HEMT manage as enhancement mode;
5) grow N+ type GaAs thickness and be about 300nm, doping content is 3.5 × 10
18cm
-3;
6) mesa etch isolation active area;
7) grown silicon nitride;
8) photoetching silicon nitride layer, carves source-drain electrode territory, carries out N+ ion implantation, forms source electrode and drain electrode, removes silicon nitride;
9) apply photoresist, the photoresist of electrode contact locations is removed in photoetching;
10) vacuum evaporation gold germanium nickel/gold;
11) peel off, alloying forms source, leaks Ohm contact electrode;
12) apply photoresist, the photoresist of gate location is removed in photoetching;
13) growth thickness is 0.5 μm of Ti/Pt/Au;
14) remove the metal on photoresist and photoresist, form the grid of Schottky contacts;
15) apply photoresist, make lead-in wire by lithography, the window in drop-down pole plate and clamped beam anchor district;
16) Au that a layer thickness is 0.3 μm is grown;
17) remove photoresist, form the anchor district of lead-in wire, drop-down pole plate, clamped beam;
18) depositing insulating layer, application epitaxy technique grows the Si of 0.1 μm
xn
1-xinsulating barrier;
19) unnecessary insulating barrier is removed in photoetching, only retains the insulating barrier above drop-down pole plate;
20) form PMGI sacrifice layer by spin coating mode, then photoetching sacrifice layer, only retain the sacrifice layer below clamped beam;
21) down payment of one deck for electroplating is grown: evaporation Ti/Au/Ti, as seed layer thickness 50/150/30nm;
22) apply photoresist, make clamped beam by lithography, the window of anchor district and connecting line;
23) electroplate one deck gold, its thickness is 2 μm;
24) remove photoresist, remove the layer gold on photoresist simultaneously;
25) anti-carve titanium/gold/titanium, corrosion Seed Layer, formed clamped beam and and connecting line;
26) polyimide sacrificial layer is removed, release MEMS clamped beam;
27) HEMT of preparation is connected with external circuit, forms frequency multiplier.
Whether distinguish is that the standard of this structure is as follows:
The two clamped beam switch double grid HEMT frequency multiplier of GaAs base low-leakage current of the present invention, two grids are set up in parallel, and two clamped beam switches are suspended on two grids respectively by anchor district.Reference signal and feedback signal are carried on two clamped beam switches respectively by anchor district.Closed or the off-state of clamped beam switch is controlled by direct current biasing, and actuation voltage is designed to the threshold voltage of HEMT.When clamped beam switch disconnects, gate voltage is 0, HEMT cut-off.When two clamped beam switches all close with gate contact by direct current biasing is drop-down, two-dimensional electron gas raceway groove is formed, HEMT conducting, reference signal is multiplied by HEMT with feedback signal, drain electrode output packet is containing the phase information of two signals, through low pass filter, the circulation of voltage controlled oscillator, divider feedback, final voltage controlled oscillator exports the frequency signal that reference signal is multiplied by N.In addition, drop-down closed single clamped beam switch can realize the amplification to individual signals, and meanwhile, another is not formed high resistance area by below drop-down closed clamped beam switch, effectively can improve the reverse breakdown voltage of HEMT.