Composition for InSB and GaAs thin film on silicon substrate for use in photodetectors

DETAILED DESCRIPTION OF THE INVENTION When growing InSb or GaAs by MOCVD or MBE, all ingredients and operating conditions are maintained very clean and purity is absolutely necessary.
Superclean semi-insulating silicon is used as a substrate.
As a first step when preparing an InSb photodetector, an InSb layer is grown on the substrate.
Referring to FIG.
1, pure H.
sub.
2 (99.
9999%) is bubbled through solution 10 containing the precursor Indium source, such as trimethyl indium or triethyl indium which is maintained at 0.
degree.
-18.
degree.
C.
, preferably 18.
degree.
C.
at 1.
5 l/min.
The H.
sub.
2 gas flow containing the dilute vapor solution of the indium precursor is transported at or near room temperature to the hot substrate 41.
H.
sub.
2 is also bubbled through the Sb source 20, i.
e.
, a liquid solution of the precursor trimethylantimony or triethylantimony.
The dilute vapor solution of the antimony precursor is transported through line 30 to the substrate chamber 40 where substrate 41 is mounted.
Substrate 41 is silicon, as stated above.
The temperature of substrate 41 may be kept from 400.
degree.
C.
to 500.
degree.
C.
, and preferably at 480.
degree.
C.
for purposes of this invention.
The pressure throughout the growth procedure of the substrate chamber is maintained at low pressures of 50-100 torr, preferably at 76 torr.
Unreacted gas and vapor are exhausted through line 31, or through filter 32 to molecular sieve trap 33 to exhaust.
The In and Sb precursor vapors are transported to the substrate for a given period of time to achieve a desired thickness, which may range from 10 A.
degree.
to the desired thickness of 0.
5-2 .
mu.
m, or higher.
Generally, maintenance of the flow of the precursors for 1/2 hour is sufficient to reach the desired thickness of 0.
5 .
mu.
m.
After the first layer of InSb is grown, the layer is doped through inlets 21-24 which are used to permit the entry of gases such as disilane, H.
sub.
2 S, dimethyl selenium, (H.
sub.
2 Te) or (H.
sub.
2 Sn), for n-type doping.
Pure H.
sub.
2 or N