Far infrared Ga/sub 1-x/In/sub x/Sb/InAs-based strained-layer superlattice detectors grown by OMVPE

Strained-layer, type-II Ga/sub 1-x/In/sub x/Sb/InAs superlattice detectors operating at 9 /spl mu/m have been grown for the first time by OMVPE. In all reported literature thus far, MBE has been exclusively used to grow this particular material system. In the present research, the material was grown by an atmospheric pressure OMVPE reactor using high purity metallorganic precursors (TM Ga, TMSb, TMIn and TBAs). A 300 /spl Aring/ of Ga/sub 1-x/In/sub x/Sb buffer layer was grown on n-GaAs(100) substrate followed by 20 periods (60 /spl Aring/ Ga/sub 0.6/In/sub 0.4/Sb/60 /spl Aring/ InAs) superlattice. A 300 /spl Aring/ InAs was grown as the capping layer. The growth took place at 600/spl deg/C with a precracker temperature of 140/spl deg/C. The absorbance characteristics measured by FTIR showed a shift in the cutoff wavelength /spl lambda/ from 1.8 /spl mu/m to 2.5 /spl mu/m when the In mole fraction was varied from 0.1 to 0.4 in Ga/sub 1-x/In/sub x/Sb layer. The use of InAs in Ga/sub 0.6/In/sub 0.4/Sb/InAs structures introduces strain and /spl lambda/ shifts from 2.5 /spl mu/m to 9 /spl mu/m as confirmed by FTIR. An increase in the number of superlattice periods (from 5 to 20) resulted in an enhanced absorbance edge. p-n photodiodes were fabricated by establishing AuGe/Ni/AuGe contacts on InAs and n-GaAs. The samples were sintered at 430/spl deg/C for 10 minutes in N/sub 2/ ambient. The samples were measured to show good I-V and R-V characteristics. The detector was edge-excited using white light to show change in conductance. The measured leakage current (1 mA