Characterization of IV-VI semiconductor materials and devices by Fourier transform infrared spectroscopy.

Abstract

Emissions from a commercial IV-VI semiconductor PbEuSe diode laser were also obtained using a modular type MR spectrometer. The laser exhibits wide (up to 4 cm-1) continuous wave, single-mode tuning regions between 90 K to 116 K for currents in the range of 400 mA to 1000 mA. This type of mid-IR laser characterization is very useful for designing laser-based molecular spectroscopy instrumentation.

Transmission and photoluminescence properties of IV-VI semiconductor materials grown by molecular beam epitaxy (UBE) and liquid phase epitaxy (LPE) were characterized using a vacuum-bench type Fourier transform infrared (FTIR) spectrometer. Samples for transmission measurements included Pb1-x EuxSe (x = 0%, 2.44%, 7.32%) and Pb1-xSr xSe (x = 0%, 7.83%, 15.7%, 26.1%) grown by MBE on Si(111) and BaF 2(111) substrates, respectively. Pb1-xSnxSe (x = 0%, 3%, 5%, 6%, 7%, 10%) samples grown by LPE on MBE-prepared Si(100) substrates were also measured. Fundamental absorption edge energies for these alloys were derived from the transmission spectra and their dependence on composition and temperature were reported. Refractive indices for Pb 1-xSrxSe were calculated based on the interference data. Effects of alloy disorder, impurity and free-carrier absorption, and cryogenic cycling are observed in the transmission spectral data. Photoluminescence experiments performed on LPE-grown PbSe, PbTe, PbSeTe, and PbSnSeTe (liquid tin contents of 5% and 40%) epilayers show unusual, strong, and above bandgap emissions at temperatures ranging from cryogenic to above room temperature. These emissions may be the first direct experimental observation of defect states associated with anion (chalcogen) vacancies theorized three decades ago. These measurements provide useful information for designing structures that will be used for fabrication of mid-IR lasers.