MOLECULAR-BEAM EPITAXY OF CDTE ON LARGE AREA SI(100)

We have grown CdTe directly on 2- and 5-in. diam Si(100) by molecular-beam epitaxy and characterized the layers by in situ reflection high-energy electron diffraction, double crystal x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and low-temperature photoluminescence. The films are up to 10-mu-m thick and mirror-like over their entire surface. Even on 5-in. diam wafers, the structural and thickness uniformity is excellent. Two domains, oriented 90-degrees apart, are observed in the CdTe films on oriented Si(100) substrates, whereas single-domain films are grown on Si(100) tilted 6-degrees or 8-degrees toward [011]. The layers on misoriented substrates have better morphology than those on oriented Si(100), and the substrate tilt also eliminates twinning in the CdTe layers. First attempts to grow HgCdTe on Si(100) with a CdTe buffer layer have produced up to 10-mu-m thick layers with cutoff wavelengths between 5 and 10-mu-m and with an average full width at half-maximum of the double-crystal x-ray diffraction peaks of 200 arc s.