Abstract
This paper summarizes progress in metal organic chemical vapour deposition (MOCVD) technology achieved in recent years at the Institute of Applied Physics, Military University of Technology and VIGO System S.A. MOCVD with a wide range of composition and donor/acceptor doping and without post-growth annealing is a very convenient tool for the deposition of HgCdTe epilayers used for uncooled infrared detectors. Particular attention is focused on: surface morphology improvement, doping issues, diffusion processes during growth study, substrate issues, crystallographic orientation selection. In this respect, MOCVD technology improvement influencing IR detector parameters is shown. CdTe buffer layer deposition allows HgCdTe heterostructure growth on GaAs substrates. Theoretical modelling using APSYS platform supports designing and better understanding of the carrier transport mechanism in detector’s structures. Secondary ion mass spectrometry profiles allows to compare projected and obtained structures and revealed diffusion processes of the elements. A wide range of different types of infrared detectors operating at high operating temperature conditions has been constructed: photoresistors, non-equilibrium photodiodes, dual-band photodiodes, barrier and multiple detectors. The methodical research efforts contributed to the time constant reduction are important in many detector applications. Future challenges and prospects are also discussed.
Highlights
Because infrared (IR) radiation is common in nature and a wide range of IR detector applications in almost all spheres of human activity, there is constant development of science and technology on IR sensing
The progress in IR detector technology has been associated mainly with semiconductor IR detectors, which are included in the group of photon (Received January 8, 2020; accepted July 29, 2020; published online August 24, 2020)
Cryogenic cooling was always a serious obstacle to widespread applications of IR detectors and increasing their operating temperature without detectivity deterioration has become a major challenge for many research laboratories.[2]
Summary
Because infrared (IR) radiation is common in nature and a wide range of IR detector applications in almost all spheres of human activity, there is constant development of science and technology on IR sensing. Dark current suppressing without impeding the photocurrent flow is the main idea of barrier detectors.[22] Contrary to the III–V semiconductorbased heterostructures, HgCdTe material does not exhibit a near zero valance band offset, which is the key issue limiting the performance of barrier detectors nBn type.[23] the proper p-type doping of the barrier layer may reduce the valence bandoffset and increase the offset in the conduction band allowing the photogenerated carriers to flow freely in the HgCdTe material.[24] As an example of developed HgCdTe barrier detectors, the n+p+BppN+ heterostructure for the MWIR range is presented It consists of a low p-type doped (p) absorber, widebandgap heavily doped p-type unipolar barrier (Bp) and heavily doped contacts. The cut-off wavelength kCO of measured detector moves to longer wavelengths with decreasing the temperature because the energy gap is narrower there
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