MBE GROWTH AND CHARACTERIZATION OF Pb-SALT SEMICONDUCTORS FOR MID-INFRARED DETECTOR AND LASER APPLICATION

Abstract

IV-VI semiconductors grown by molecular beam epitaxy (MBE) on various substrates are extensively attractive for mid-infrared optoelectronic device application. The main goal of this research is to improve device performance by lowering defects densities in the epitaxial layers during MBE growth of Pb-salt materials on a lattice-mismatched substrate. Most of the work is based on MBE growth of monocrystalline PbSe on Si (111) substrates. Details of experiments are described and supported by reflection high-energy electron diffraction (RHEED) patterns. The effect of the in-situ surface treatment methods with a motivation of improving electrical and morphological properties of epilayers is demonstrated.

A detailed study on surface morphologies and chemical composition of growth pits and dislocations in PbSe epilayers is provided. Various growth defects are investigated by scanning electron microscopy (SEM) and energy-dispersive x-ray analysis (EDXA). Through a series of experimental studies, it has been confirmed that the vast majority of growth pits within PbSe epilayers contains either single or multiple PbSe microcrystals with a distinct cuboid shape.

Lead salt mid-infrared optoelectronic devices are fabricated on various substrates. Several other research works include: (1) Edge-emitting infrared lasers on BaF2 (110) substrates. A method of substrate transfer from a BaF2 substrate to a copper heat-sink is developed. Pulsed photoluminescence (PL) measurements are conducted with help of Fourier transform infrared (FTIR) spectroscopy method during every single step of device processing. (2) Mid-infrared detectors on silicon (111) substrates. Single-element PbSnSe infrared detectors have been made on CaF2 /Si (111) heterostructures; I-V measurement is accomplished on these detectors.