MOLECULAR-BEAM EPITAXIAL-GROWTH OF HGCDTE MIDWAVE INFRARED MULTISPECTRAL DETECTORS

Molecular beam epitaxy (MBE) has beep utilized to fabricate high perfo rmance HgCdTe infrared detectors with sensitivity to midwave infrared radiation in adjacent spectral bands for two-color thermal imaging app lications. Growth of a multilayer HgCdTe device structure by MBE enabl es the use of an n-p-n device architecture that facilitates pixel-leve l registration of images in two separate spectral bands. Device struct ures were grown on CdZnTe(211)(B) substrates using CdTe, Te, and Hg so urces with in situ In and As doping. The composition of the HgCdTe all oy layers was adjusted to achieve detection of infrared radiation in a djacent spectral bands in the 3.5-4.5 mu m wavelength range. As-grown device structures were characterized with x-ray diffraction, wet chemi cal defect etching, and secondary ion mass spectrometry. Mesa type dev ices were patterned using reactive ion etching and ohmic contacts were made to the two n-type layers for operation of the detectors in a seq uential detection mode. The spectral response characteristics of the d evices are highly uniform across a 64x64 element array, with standard deviation in cutoff wavelength less than 0.01 mu m and external quantu m efficiencies greater than 70% in both bands. Sharp detector cutoffs enable spectral crosstalk less than 1% to be obtained for spectral ban ds with as little as 0.6 mu m separation. Junction reverse-breakdown v oltages in excess of 500 mV and 80 K dynamic resistance-area products for each component diode in excess of 1x10(6) Omega cm(2) at +/-100mV operating bias have been demonstrated. (C) 1998 American Vacuum Societ y.