JP2876749B2 - Semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor device having a field effect transistor structure.

[Conventional technology]

InP semiconductors have attracted attention as high-output and high-frequency device materials because of their good thermal conductivity and high electron saturation speed. However, since good Schottky characteristics cannot be obtained with InP, research on MISFETs (insulated gate field effect transistors) has been more active than MESFETs (Schottky junction field effect transistors). This MISFET
As shown in FIG. 3 (a), for example, an InP crystal layer 6 is formed on an InP substrate 1, and a source electrode 2, a drain electrode 3, and a gate formed on an insulating film 4 thereon. An electrode 5 is provided.

On the other hand, so-called modulation doping, such as GaAs-based HEMT (High Electron Mobility Transistor), in which only one of the different types of bonded semiconductors is selectively doped, has been attempted with a combination of AlInAs / InP. ing. For example, as shown in FIG. 3B, an InP buffer layer 7 and an n-AlInAs layer 8 are laminated on an InP substrate 1, and a source electrode 2, a drain electrode 3 and a gate electrode 5 are provided thereon. I have.

In this case, the electron concentration can be controlled by changing the doping concentration or the gate voltage.

[Problems to be solved by the invention]

Although SiO ₂ or Al ₂ O ₃ is used as the insulating film 4 of the InP-MISFET shown in FIG. 3A, there are many interface states, and there is a problem that hysteresis and current drift are large. there were.

In the InP-HEMT shown in FIG. 3 (b),
Poor compatibility between P element and Al element at InP / AlInAs interface
There has been a problem that a semiconductor device using high mobility electrons as carriers, such as As-HEMT, cannot be obtained.

Accordingly, the present invention provides a semiconductor device having good high-frequency characteristics and capable of high-output operation.

[Means for solving the problem]

The present invention provides a semiconductor device having a field-effect transistor structure using semi-insulating InP, wherein semi-insulating InP is used.
An undoped InP buffer layer, an n-InP layer, an undoped InGaAs layer, and an undoped AlInAs layer are sequentially stacked on a P substrate, and a gate electrode is provided on the undoped AlInAs layer.

Further, the carrier concentration and thickness of the n-InP layer are set so that electrons remain in the n-InP layer even when electrons are supplied to the undoped InGaAs layer, and the thickness of the undoped InGaAs layer is n-InP. The layer side and the quantum well formed from the undoped AlInAs layer side may be set to overlap.

[Action]

According to the present invention, since the gate electrode is provided on the undoped AlInAs layer, good Schottky characteristics can be obtained with an FET using InP as a substrate. Also undoped
The thickness of the InGaAs layer is set so that the undoped AlInAs layer side and the quantum well formed on the n-InP layer side overlap, so that the two-dimensional electron gas generated at the heterogeneous interface is located at the same location. Therefore, the carrier can be controlled by the gate voltage.

〔Example〕

FIG. 1A is a cross-sectional view of an element of an InP-FET according to an embodiment of the present invention. As shown in this figure, on an InP substrate 1, an InP buffer layer 7, an n-InP layer 9, an undoped InGaAs layer
10, an undoped AlInAs layer 11 is sequentially stacked, and a source electrode 2, a drain electrode 3,
And a gate electrode 5 are formed. Each of the above crystal layers can be formed by a method such as MBE (molecular beam epitaxy) or OMVPE (metal organic chemical vapor deposition).

The operating layer in this device structure includes a two-dimensional electron gas 12 formed at the interface between the n-InP layer 9 and the undoped InGaAs layer 10 shown in FIG. 1B, and a carrier 1 remaining in the n-InP layer 9.
3 Since the undoped InGaAs layer 10 has a high electron mobility in a low electric field, it is effective to lower the parasitic resistance Rs. Further, since the AlInAs layer 11 on the surface side is undoped, the Schottky characteristic is better than that of the doped AlInAs layer. Therefore, when a positive voltage is applied to the gate electrode 5, the undoped AlInAs layer 11 and the undoped InGaAs layer 10
The two-dimensional electron gas can also be stored at the interface of the substrate, and the current driving capability can be increased. At this time, undoped InGaAs
If the thickness of the layer 10 is large, the two-dimensional electron gas 12 is distributed in two quantum wells as shown in FIG. However, the thickness of the undoped InGaAs layer 10 is
By setting the quantum well formed on the undoped AlInAs layer 11 side to overlap the two-dimensional electron gas 12 formed from the heterogeneous interface, as shown in FIG. it can. Therefore, it is advantageous when controlling carriers by the gate voltage.

Also, as the drain voltage is increased, the electrons themselves have a higher energy, and in particular, the undoped In
The electrons in the GaAs layer 10 cross over the barrier at the heterogeneous interface and the n-InP layer 9
Although the electrons also flow into the side, the saturation speed of electrons in the n-InP layer 9 is higher than the saturation speed in the undoped InGaAs layer 10, so that the performance does not deteriorate.

In the case of the n-InP layer 9 as a specific condition in this embodiment,
Even if carriers are supplied to the undoped InGaAs layer 10, it is necessary to have a carrier concentration and a thickness such that carriers still remain. For example, the carrier concentration is 3 × 10 ¹⁸ / cm 3
A thickness of 100 mm is appropriate for ³ and can be controlled by a Schottky electrode provided on the undoped AlInAs layer 11. Next, as for the undoped InGaAs layer 10, the undoped A
It is necessary that the two-dimensional electron gas formed on the lInAs layer 11 has a thickness such that it is located at the same position. Therefore, for example, a carrier concentration of 1 × 10 ¹⁵ / cm ³ or less and a thickness of 50 to 1
00Å is appropriate. On the other hand, the undoped AlInAs layer 11 suitably has a carrier concentration of 1 × 10 ¹⁵ / cm ³ or less and a thickness of 300 °.
Of course, undoped AlInAs layer 11 to reduce source resistance
An n ⁺ InGaAs layer is stacked on the n ⁺
InGaAs may be removed.

〔The invention's effect〕

According to the present invention, good Schottky characteristics can be obtained with an FET using an InP substrate, and the density of generated two-dimensional electron gas can be controlled. Further, since the two-dimensional electron gas is accumulated at the interface between the two different kinds, the electron concentration can be easily increased, and therefore, the current density can be increased. Moreover, in a high electric field, a large amount of electrons are distributed on the InP side, so that high-frequency characteristics are good. Further, since the InP substrate is used, the heat radiation effect is high, and it is effective when used as a high-output element in a microwave or millimeter wave band.

[Brief description of the drawings]

FIG. 1 is a view showing a structure of a semiconductor device according to an embodiment of the present invention, FIG. 2 is a view showing a two-dimensional electron position depending on the thickness of an undoped InGaAs layer, and FIG. is there. DESCRIPTION OF SYMBOLS 1 ... InP substrate, 2 ... Source electrode, 3 ... Drain electrode, 4 ... Insulating film, 5 ... Gate electrode, 6 ... InP crystal layer, 7 ... InP buffer layer, 8 ... n-AlInAs Layer, 9 ... n
-InP layer, 10 ... Undoped InGaAs layer, 11 ... Undoped
AlInAs layer, 12 two-dimensional electron gas, 13 carriers.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/337-21/338 H01L 27/095 H01L 27/098 H01L 29/775-29/778 H01L 29 / 80-29/812

Claims (1)

(57) [Claims] 1. A semiconductor device having a field effect transistor structure using a semi-insulating InP (indium phosphorus) substrate, wherein an undoped InP buffer layer, an n-InP
Layer, undoped InGaAs (indium gallium arsenide)
Layers and an undoped AlInAs (aluminum indium arsenide) layer are sequentially laminated, a Schottky electrode is provided on the undoped AlInAs layer, and the carrier concentration and the thickness of the n-InP layer are the same as those of the undoped InGaAs layer. The thickness of the undoped InGaAs layer is set such that the n-InP layer side and the quantum well formed from the undoped AlInAs layer side overlap even when electrons are supplied. A semiconductor device characterized by being performed.