Status of HgCdTe-MBE technology for producing dual-band infrared detectors

Progress on achieving reproducible growth of high performance, dual-band IR detector structures in HgCdTe grown by molecular beam epitaxy (MBE) is described. The reproducibility achieved in the MBE growth of n-p-n device structures comprising HgCdTe epitaxial layers with different composition and doping characteristics was evaluated from the run-to-run precision in the alloy composition, dopant concentration and dislocation density. For a series of 25 growth runs. the standard deviation of the alloy composition in the n-type absorbing layer was 0.002; the yield for the in situ n- and p-type doping process was > 95%; and the average dislocation density was < 5 x 10(5) cm(-2). In situ optical diagnostics, including spectroscopic ellipsometry and an optical absorption flux monitor were used for the real-time determination of the alloy composition and Cd flux during MBE growth of the two-color device structures. Focal plane arrays with 128 x 128 elements were fabricated for the simultaneous detection of two sub-bands in the MWIR spectrum. Average R(o)A values exceeding 1 x 10(6) and 2 x 10(5) Ohm cm(2) were measured at 77 K for diodes operating at 4.0 and 4.5 mu m, respectively, and the quantum efficiency was greater than 70% in each band. These results on MBE growth and device performance demonstrate that HgCdTe MBE technology is poised for the modest-scale production of advanced IR devices. (C) 2000 Elsevier Science B.V. All rights reserved.