INTEGRATED MULTISENSOR CONTROL OF II-VI MBE FOR GROWTH OF COMPLEX IR DETECTOR STRUCTURES

Next-generation HgCdTe infrared detectors and detector arrays require the growth of multilayer heterojunction structures with precisely cont rolled alloy composition and doping levels and minimal defect densitie s. Molecular beam epitaxy (MBE) provides the ability to produce such s tructures. However, in the absence of a real-time, in situ, control me thodology the extreme sensitivity of BgCdTe layer quality and doping e fficiency on fundamental MBE variable such a substrate temperature and effusion cell flux provide serious challenges to the uniform and repr oducible growth of such structures. In this paper, we describe an inte grated, multi-sensor approach for monitoring and controlling the varia bles that are most important for MBE growth of HgCdTe device structure s used in advanced multi-color infrared detectors and high speed, low- noise avalanche photodiodes. Substrate temperature, effusion cell flux , and layer composition are monitored using absorption-edge spectrosco py (ABES), optical flux monitoring (OFM), an spectroscopic ellipsometr y (SE), respectively. Flexible, custom software has been developed and implemented for analysis of sensor inputs and feedback control of the MBE system in response to those inputs. The sensors and their applica tion to growth of HgCdTe will be described, and the use of a custom so ftware framework for data analysis and system control will be discusse d.