III-V semiconductor structure and its producing method

Details III-V semiconductor structure and its producing method III-V semiconductor structure and its producing method

1999-02-09

2001-03-13

Bowers, Charles (Department: 2813)

Semiconductor device manufacturing: process

Forming schottky junction

Compound semiconductor

C438S573000

Reexamination Certificate

active

06200885

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a III-V semiconductor structure and its producing method.
BACKGROUND OF THE INVENTION
The metal/semiconductor Schottky junction of a III-V Schottky diode has the characteristics of a monocarrier and a fast switching speed, and can be used in the fields of photoelectric and microwave applications. However, the surface conditions of the III-V Schottky diode, such as the impurity content and surface free radicals, will influence its barrier hight. The energy barrier of a Schottky diode is called the Schottky barrier. If the surface defects of the diode can be minimized, the Schottky barrier height will be increased and the diode will be more useful. Please refer to
FIG. 1
showing a conventional structure of a Schottky diode. The diode includes a metal layer
1
, a Schottky barrier layer
2
, and a substrate
3
. The metal layer
1
is usually made of a noble metal for conducting the electricity. The Schottky barrier layer
2
is a thin aluminum layer sputtered on the substrate
3
. Conventionally, it has been found that the Schottky barrier height can effectively increase after treating the substrate with a solution containing sulfur ions. However, the sulfur ion in the surface of the substrate will evanesce off after using it for a period of time or after working under a high temperature. Then, the Schottky barrier height will be lowered again. Another method disclosed that the Schottky barrier can also be increased after treating the substrate with aluminum fluoride solution (AlF
3
), but the ideality factor of this method is too high to be applied in the industry. (see J. Applied Physics, Vol. 78, p. 291 (1995))
Accordingly, the present invention provides an easy and economical method for producing a III-V Schottky diode and provides a new diode structure. This method quite useful for every kind of III-V semiconductor structure.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a III-V semiconductor structure having a Schottky barrier. The structure includes a Ill-V substrate, a Schottky barrier layer formed on the III-V substrate by reacting the III-V substrate with sulfate ions, and a metal layer formed on the Schottky barrier layer.
Preferably, the III-V substrate is made of one selected from a group consisting of InP, GaAs, InGaAs, InGaP, InGaAsP, InAs, and InSb, and the metal layer is made of one selected from a group consisting of Au, Ag, Ni, Pt, and Pd.
In an embodiment of the present invention, the Schottky barrier layer is a single layer made of Al
2
(SO
4
)
3
and ln
2
(SO
4
)
3
. In another embodiment of the present invention, the Schottky barrier layer includes two layers, a first barrier layer made of AlInP on the Ill-V substrate and a second barrier layer made of Al
2
(SO
4
)
3
on the first barrier layer.
Another object of the present invention is to provide a method for forming a Ill-V semiconductor structure having a Schottky barrier layer.
The method includes (a) providing a III-V substrate, (b) treating the Ill-V substrate with a sulfuric acid solution, (c) forming a Schottky barrier layer on the III-V substrate, and (d) forming a metal layer on the Schottky barrier layer.
In accordance with the present invention, the sulfuric acid solution has a concentration ranged from 50 to 75 vol. %. The Schottky barrier layer is formed by coating an aluminum layer having a thickness ranged from 30 to 70 Å on the treated III-V substrate, and the aluminum layer is coated by a method selected from a group consisting of evaporation, sputtering, deposition, plating, and electroplating. After the step (b), the method further includes a step of drying the III-V substrate by a nitrogen gas.
A further object of the present invention is to provide a method for forming a III-V semiconductor structure having a Schottky barrier layer.
The method includes (a) providing a Ill-V substrate, (b) forming a first barrier layer on the Ill-V substrate, (c) treating the first barrier layer with a sulfuric acid solution, (d) forming a second barrier layer on the first barrier layer, and (e) forming a metal layer on the second barrier layer.
Preferably, the first barrier layer is an AlInP layer formed by coating an aluminum layer on the III-V substrate, and the second barrier layer is an Al
2
(SO
4
)
3
layer formed by coating another aluminum layer on the treated first barrier layer. Before the step (b), the method further includes a step of cleaning the III-V substrate. After the step (c), the method further includes a step of drying the second barrier layer by a nitrogen gas.
The present invention may best be understood through the following description with reference to the accompanying drawings, in which:


REFERENCES:
patent: 4211587 (1980-07-01), Massies et al.
patent: 5221638 (1993-06-01), Ohtsuka et al.
patent: 5627090 (1997-05-01), Marukawa et al.

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