High performance infrared (IR) sensing and imaging systems require IR optoelectronic detectors that have a high signal-to-noise ratio (SNR) and a fast response time, and that can be readily hybridised to CMOS read-out integrated circuits (ROICs). From a device point of view, this translates to p-n junction photovoltaic detectors based on narrow bandgap semiconductors with a high quantum efficiency (signal) and low dark current (noise). These requirements limit the choice of possible semiconductors to those having an appropriate bandgap that matches the wavelength band of interest combined with a high optical absorption coefficient and a long minority carrier diffusion length, which corresponds to a large mobility-lifetime product for photogenerated minority carriers. Technological constraints and modern clean-room fabrication processes necessitate that IR detector technologies are generally based on thin-film narrow bandgap semiconductors that have been epitaxially grown on lattice-matched wider bandgap IR-transparent substrates. The basic semiconductor material properties have led to InGaAs (in the SWIR up to 1.7 microns), InSb (in the MWIR up to 5 microns), and HgCdTe (in the eSWIR, MWIR and LWIR wavelength bands) being the dominant IR detector technologies for high performance applications. In this paper, the current technological limitations of HgCdTe-based technologies will be discussed with a view towards developing future pathways for the development of next-generation IR imaging arrays having the features of larger imaging array format and smaller pixel pitch, higher pixel yield and operability, higher quantum efficiency (QE), higher operating temperature (HOT), and dramatically lower per-unit cost.
HgCdTe has dominated the high performance end of the IR detector market for decades. At present, the fabrication costs
of HgCdTe based advanced infrared devices is relatively high, due to the low yield associated with lattice matched
CdZnTe substrates and a complicated cooling system. One approach to ease this problem is to use a cost effective
alternative substrate, such as Si or GaAs. Recently, GaSb has emerged as a new alternative with better lattice matching.
In addition, implementation of MBE-grown unipolar n-type/barrier/n-type detector structures in the HgCdTe material
system has been recently proposed and studied intensively to enhance the detector operating temperature. The unipolar
nBn photodetector structure can be used to substantially reduce dark current and noise without impeding photocurrent
flow. In this paper, recent progress in MBE growth of HgCdTe infrared material at the University of Western Australia
(UWA) is reported, including MBE growth of HgCdTe on GaSb alternative substrates and growth of HgCdTe nBn
structures.
A theoretical calculation result of Hg1-xCdxTe (x=0.3) avalanche photodiodes (APDs) based on PIN structure is
obtained in the paper, which has a ratio of ionization factor k=0.06. The energy dispersion factor and the threshold
energy are acquired according to the parameters of material. And the gain, as well as the breakdown voltage, is obtained.
The composition, thickness, doping level is calculated theoretically to get an optimized APD device.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.