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Tunable, mid-infrared radiation was obtained by frequency doubling of a continuous-wave CO(2) laser in orientation-patterned GaAs crystal. Active cooling of the crystal minimized pump-induced thermal effects, allowing generation of output powers exceeding 300 mW across the wavelength range of 4.63-4.78 μm.

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We report the observation of multiple photoluminescence peaks due to monolayer thickness fluctuations in HgTe-CdTe superlattices. The spectra for seven different [211]-oriented superlattices with band gaps varying from 133 to 495 meV exhibit double peaks, and in nearly all cases the energy splitting corresponds to a difference of ≊1.5 ML in the quantum well thickness.

Scanning tunneling microscopy is demonstrated for determining the surface morphology of etched Hg-based semiconductors. Wet etching of HgTe/CdTe superlattices used a Br-based etch solution while dry etching used methyl-free radicals formed by electron cyclotron resonance in a reactive ion etching reactor. Both techniques produced smooth surfaces with random features over large regions. Features ranged in height from 1 to 5 nm for wet etching, while the smoothest dry etched sample had random features with an average height of 40 nm. Near mesa structures, evidence of differential etching was observed between the different composition layers in the HgTe/CdTe superlattices for both wet and dry etched samples.