IV-VI semiconductor growth on silicon substrates and new mid-infrared laser fabrication methods

This paper reviews results from research conducted at the University of Okl ahoma on the development of new IV-VI semiconductor (lead salt) epitaxial g rowth and laser fabrication procedures that can ultimately lead to dramatic increases in mid-IR laser operating temperatures. Work has focused on grow th of IV-VI semiconductor laser structures on silicon substrates using buff er layers that contain BaF2. Recent experiments show that it is possible to obtain high crystalline quality IV-VI semiconductor layer structures on (1 11)-oriented silicon substrates using molecular beam epitaxy (MBE) or on (1 00)-oriented silicon using a combination of MBE and liquid phase epitaxy (L PE). Experimental data for IV-VI semiconductor layer structures grown on si licon substrates including crystalline quality information as determined by high resolution X-ray diffraction (HRXRD) measurements and absorption edge information as determined by Fourier transform infrared (FTIR) transmissio n measurements are presented. Results show that these materials can be used to fabricate lasers that cover the 3 mu m (3333 cm(-1)) to 16 mu m (625 cm (-1)) spectral range. Removal of IV-VI semiconductor laser structures from the silicon growth substrate by dissolving BaF2 buffer layers with water is also demonstrated. This allows epitaxially-grown laser structures to be sa ndwiched between two heat sinks with a minimum of thermally resistive IV-VI semiconductor material. Theoretical modeling predicts that IV-VI lasers fa bricated this way will have maximum continuous wave (cw) operating temperat ures at least 60 degrees higher than those of IV-VI lasers fabricated on Pb Se or PbTe substrates. (C) 1999 Elsevier Science B.V. All rights reserved.