JPH01207979A - Compound semiconductor device - Google Patents

Abstract

PURPOSE:To obtain low contact resistance easily, by forming ohmic contact through a highly concentrated layer on a two dimensional electronic gas region. CONSTITUTION:n<+> type GaAs layers 6a and 6b are formed between source and drain electrodes 1 and 3 as well as non-doped GaAs layer 5 respectively. A two dimensional gas region 7 is in existence between the n<+> type GaAs layers 6a and 6b of 0.5mum thickness. As the above layers 6a and 6b are formed as the third semiconductor layers on the non-doped GaAs layer 5 which is the first semiconductor layer, ohmic contact having low contact resistance is formed easily on the surface of the layers 6a and 6b. Resistance between the n<+> type GaAs layers and the two dimensional electronic gas region 7 is so small that a compound semiconductor having low resistance between the gate and source electrodes is obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a compound semiconductor device.

[Conventional technology]

FIG. 2 is a cross-sectional view of an example of a conventional compound semiconductor device.

The compound semiconductor device includes an undoped GaAs layer 5 which is a first semiconductor layer on a semi-insulating GaAs layer, and an A I! layer which is a second semiconductor layer. (1-x) G a
A heterojunction is formed at the interface between the electrode 4 and the drain electrode 3, and a two-dimensional electron gas region 7 with high mobility is formed within the dotted line below the surface of the undoped GaAs layer 5.

In order to form a low resistance ohmic layer under the source and drain electrodes 1 and 3, the electron supply layer A13...
・Ohmi-2 metal was vapor-deposited on the surface of GM layer 4, and a low-resistance alloy layer was formed by heat treatment.

[Problem to be solved by the invention]

The above-described compound semiconductor device has a problem in that it is not necessarily easy to form an ohmic contact on the surface of the electron supply layer, and a stable low contact resistance cannot be obtained.

Even if one chooses the best material for the two-dimensional electron gas mobility, electron concentration, etc. from various materials for the electron supply layer,
There are also cases where the above-mentioned ohmic contacts 1 to 1 cannot be formed, and there is also the drawback that any crystal can not always be used as the electron supply layer.

[Means to solve the problem]

In the compound semiconductor device of the present invention, a second semiconductor layer having a different electron affinity from the first semiconductor layer is formed on the surface of the first semiconductor layer, and a high mobility two-dimensional forming a heterojunction with an electron gas region;
In a compound semiconductor device having a gate electrode on the surface of a semiconductor layer, a height higher than that of the first semiconductor layer is provided between the source and drain electrodes provided with the gate electrode in between and the first semiconductor layer. A third semiconductor layer having an impurity concentration is provided.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention.

The compound semiconductor device has a source electrode 1 and a drain electrode 3.
and the undoped GaAs layer 5, respectively.
This device is the same as the conventional compound semiconductor device shown in FIG. 2 except that layers 6a and 6b are provided.

The two-dimensional electron gas region 7 has two n+
It exists between the GaAs layers 6a and 6b. Since the n+ GaAs layer 6 is formed as the third semiconductor layer on the surface of the undoped GaAs layer 5 as the first semiconductor layer, an ohmic contact with low contact resistance can be easily formed on the surface.

Since the resistance between the n+GaAs layer and the two-dimensional electron waste region 7 is small, a compound semiconductor with low gate-source resistance can be obtained.

Note that the n4GaAs layers 6a and 6b may penetrate the undoped GaAs layer 5.

〔Effect of the invention〕

As explained above, in the present invention, a low contact resistance can be easily obtained by forming an ohmic contact in a two-dimensional electron gas region via a high concentration layer.

Therefore, a heterojunction compound semiconductor device with low source parasitic resistance can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of an example of a conventional compound semiconductor device. 1... Source electrode, 2... Gate electrode, 3... Drain electrode, 4... A I! (s-x) G a x
As layer, 5... undoped GaAs layer, 6--n
+GaAs layer, 7... two-dimensional waste region.

Claims (1)

[Claims] A second semiconductor layer having a different electron affinity from the first semiconductor layer is formed on the surface of the first semiconductor layer, and a two-dimensional electron gas region with high mobility is formed at the interface of the two semiconductor layers to form a heterogeneous semiconductor layer. In a compound semiconductor device that forms a junction and has a gate electrode on the surface of the second semiconductor layer, the source and drain electrodes provided with the gate electrode sandwiched therebetween and the first
A compound semiconductor device characterized in that a third semiconductor layer having a higher impurity concentration than the first semiconductor layer is provided between each of the semiconductor layers.