Nonequilibrium Operation of Arsenic Diffused Long-Wavelength Infrared HgCdTe Photodiodes

Abstract

We demonstrated a device with a unique planar architecture using a novel approach for obtaining low arsenic doping concentrations in long-wavelength (LW) HgCdTe on CdZnTe substrates. HgCdTe materials were grown by molecular beam epitaxy (MBE). We fabricated a p-on-n structure that we term P + /p/N + where the symbol ''p'' is to indicate a drastically reduced extrinsic p-type carrier concentration (on the order of mid 10 15 cm -3 ); P + and N + denote a higher doping density, as well as a higher energy gap, than the photosensitive base p-region. Fabricated devices indicated that Auger suppression is seen in the P + /p/N + architecture at temperatures above 130 K and we obtained a saturation current on the order of 3 mA on 250-lm-diameter devices at 300 K with Auger suppression. Data shows that about a 50% reduction in dark current is achieved at 300 K due to Auger suppression. The onset of Auger suppression voltage is 450 mV at 300 K and 100 mV at 130 K. Results indicate that a reduction of the series resistance could reduce this further. A principal challenge was to obtain low p-type doping levels in the p-region. This issue was overcome using a novel deep diffusion process, thereby demonstrating successfully low-doped p-type HgCdTe in MBE-grown material. Nearclassical spectral responses were obtained at 250 K and at 100 K with cut-off wavelengths of 7.4 lm and 10.4 lm, respectively. At 100 K, the measured nonantireflection-coated quantum efficiency was 0.57 at 0.1 V under backside illumination.

Parameter extraction of HgCdTe infrared photodiodes exhibiting Auger suppression

“…Details of the experimental device fabrication have been reported elsewhere [4]. Here we summarize the information on the devices relevant to our simulation analysis.…”

“…The background concentration in regions II and III is n-type with indium at ∼10 15 cm −3 . The ex situ p-type doping of the absorber and the top layers was achieved using arsenic implantation, followed by a deep diffusion anneal under low P(Hg) as described previously [4]. Typical SIMS profiles show an arsenic concentration in the low 10 16 cm −3 for the top layer and an arsenic concentration in the range 10 15 -10 16 cm −3 for the absorber layer.…”

“…We have previously reported a numerical device model to describe the operation of these devices [6][7][8] with details summarized in appendix A. In this work, we use our numerical device model to fit and analyse the experimental reverse bias current-voltage characteristics of LWIR Augersupressed photodiodes reported by Wijewarnasuriya et al (2008) [4].…”

“…Auger suppression translates into a negative differential resistance (NDR) in the reverse-bias currentvoltage (I -V ) characteristics, which has been experimentally observed in devices grown by metal-organic chemical vapour deposition (MOCVD) [2] and molecular beam epitaxy (MBE) using silver as an acceptor dopant [3]. More recently, Wijewarnasuriya et al (2008) [4] reported Auger suppression in LWIR MBE-grown devices using arsenic as an acceptor dopant. The carrier concentration profiles and the resulting recombination rates in these devices are highly non-uniform and space-dependent, where previous analytical models [5] of these devices offer only a limited insight.…”

MWIR and LWIR HgCdTe Infrared Detectors Operated with Reduced Cooling Requirements

“…24 Here we summarize information on the devices as relevant to our analysis. The nonequilibrium planar device structure shown in Fig.…”