Movpe Growth of MCT for LWIR Detectors

Abstract

AbstractRecent progress in the growth of Hg1−xCdxTe (MCT) by metal organic vapor phase epitaxy (MOVPE) is reviewed. The preferred diode structure for LWIR detectors is the p/n heterostructure, which requires extrinsic doping of both n and p-type layers and good compositional control of the base and cap layers. Uniform n-type doping has been demonstrated using a new precursor, TIPIn, with Auger-limited lifetime down to a doping concentration of 1 × 1015 cm−3. p-type doping has been more difficult to control because Group V dopants can occupy either Group II or Group VI sites, leading to autodoping. Some encouraging progress has been made by doping under metal rich conditions. An alternative approach to p-type doping during growth is the Rockwell-developed process of As implantation, diffusion and activation annealing, which has been used to demonstrate near diffusion-limited LWIR diodes at 77K. Major strides in the reproducibility of the MOVPE process have been achieved by in situ monitoring. Laser reflectometry has been used to monitor growth rates and morphology throughout the growth of multiple layer structures. This wafer monitoring has been complemented by system monitoring, using Epison concentration monitors and pyrometry to measure temperature.