Growth of CdGeAs/sub 2/ for mid- to far-IR frequency conversion

Summary form only given. Cadmium germanium arsenide, CdGeAs, has long been sought after as a promising frequency conversion material for the mid- to far-infrared. Its usefulness has been limited, however, but the unavailability of large, crack-free single crystals and by excessive absorption losses. We have largely overcome these difficulties using the horizontal gradient freeze growth technique. Nonwetting boat materials such as vitreous carbon or boron nitride are used to prevent secondary nucleation and sticking to the evacuated quartz ampoule, and seed crystals are used to promote monocrystalline nucleation and oriented growth. Finally, and most importantly, low temperature gradients are used to minimize stresses resulting from anisotropic thermal expansion, and a transparent furnace is used to control the seeding process and to monitor the growing crystal during the run.