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in this paper we report our latest results on the fabrication and successful operation of HgCdTe infrared diode lasers. The stripe-geometry double-heterostructure lasers were grown by molecular beam epitaxy (MBE). The active layer thickness ranges between 0.9 and 1.4 pm, and the p + and n + confinement layers were in situ doped up to 10'8cm-3 with arsenic and indium, respectively. Five double heterostructures were grown, all of which produced working lasers. The devices were operated under pulsed currents at temperatures between 40 a n d 90 K. The 77 K stimuiated emission wavelengths for these lasers were 2.9, 3.4, 3.9 and 4.4 vm. Operation at 5.3 pm was demonstrated at 60 K. The lowest 77 K threshold current density was 419 Acm-' which,is very close to the prediction of a numerical calculation. Characterization of the devices, including, lor example, temperature dependence of the threshold currents and spectral analysis, was performed and showed the characteristics of well-behaved. stable devices that operated without failure while being tested.

Spatially resolved characterization of HgCdTe materials and p-n junction diodes using scanning laser microscopy is reviewed. Several techniques that yield spatial maps of electrical inhomogeneities in HgCdTe material and non-uniformities in various performance parameters of p-n junctions fabricated using these materials have been developed. Many of the techniques are non-destructive, or can be made such with minor changes in sample preparation, and are scalable to large full wafers. A high-resolution and nondestructive techniquecalled'laserbeam inducedcurrent(~61c)'hasbeendeveiopedforspatial mapping of electrically active regions in HgCdTe. When applied to unprocessed HgCdTe material, LBIC images represent spatial distributions of electrically active defects including inclusions, strain. damage, precipitates. stacking faults, twin boundaries, dislocation clusters, bandgap and doping variations. Device structures such as p-n junctions are special cases of electrically active regions, therefore the LBIC technique lends ibeif to a nondestructive study of p n junction arrays without requiring any direct electrical contact to the individual elements of the array. The remote contacting, especially using pressure contacts, makes the application of the LBIC technique nondestructive, allowing testing at various stages of device processing to identify particular processing procedures that need optimization. LBIC has also been used to spatially map electrical non-uniformities at the HgCdTe surface near its interface with an insulating passivation layer. Besides LBIC imaging, scanning laser microscopy has been used for several other applications. For HgCdTe p-n junctions, applications include photoresponse mapping (uniformity, active area and diffusion length determination, contact bonding effects), spatially resolved light-induced degradation, and avalanche photodiode properties (ionization coefficients. localized breakdown). A key technique currently in development is the non-contact diode R d determination based on trapping mode photoconductivity. Examples of scanning laser microscopy on HgCdTe materials are infrared transmission mapping (thickness and bandgap variations), photoluminescence mapping, and minority carrier lifetime mapping (distribution of recombination centres).