Uniform low defect density molecular beam epitaxial HgCdTe

We have initiated a joint effort to better elucidate the fundamental mechanisms underlying As-doping in molecular beam epitaxy (MBE)-grown HgCdTe. We have greatly increased the As incorporation rate by using an As cracker cell. With a cracker temperature of 700°C, As incorporation as high as 4 ϫ 10 20 cm Ϫ3 has been achieved by using an As-reservoir temperature of only 175°C. This allows the growth of highly doped layers with high quality as measured by low dislocation density. Annealing experiments show higher As-activation efficiency with higher anneal temperatures for longer time and higher Hg overpressures. Data are presented for layers with a wide range of doping levels and for layer composition from 0.2 to 0.6.

Section: Methodsmentioning

confidence: 99%

Molecular beam epitaxy growth of high-quality arsenic-doped HgCdTe

Edwall

Piquette

Ellsworth

et al. 2004

“…9 This consists of a HgCdTe absorber layer doped n-type with indium and a wider bandgap cap layer. The formation of the p-on-n junction-diode is achieved by selective area ionimplantation of arsenic through a photoresist window followed by high temperature annealing for cap layer diffusion and carrier activation.…”

Section: Methodsmentioning

confidence: 99%

LWIR HgCdTe on Si detector performance and analysis

Carmody

Pasko

Edwall

et al. 2006

Self Cite

We have fabricated a series of 256 pixel 3 256 pixel, 40 mm pitch LWIR focal plane arrays (FPAs) with HgCdTe grown on (211) silicon substrates using MBE grown CdTe and CdSeTe buffer layers. The detector arrays were fabricated using Rockwell Scientific's double layer planar heterostructure (DLPH) diode architecture. The 78 K detector and focal plane array (FPA) performance are discussed in terms of quantum efficiency (QE), diode dark current and dark current operability. The FPA dark current and the tail in the FPA dark current operability histograms are discussed in terms of the HgCdTe epitaxial layer defect density and the dislocation density of the individual diode junctions. Individual diode zero bias impedance and reverse bias current-voltage (I-V) characteristics vs. temperature are discussed in terms of the dislocation density of the epitaxial layer, and the misfit stress in the epitaxial multilayer structure, and the thermal expansion mismatch in the composite substrate. The fundamental FPA performance limitations and possible FPA performance improvements are discussed in terms of basic device physics and material properties.

“…7,8 The device is composed of a narrow-bandgap n-type absorber layer (AL) and a wide-bandgap n-type cap layer (CL) in a planar configuration. The layers are grown by MBE on CdZnTe substrates with an intermediate wide-bandgap buffer layer (BL).…”

Section: Device Geometry: Double Layer Pla-nar Hetero-structurementioning

confidence: 99%

Dark Currents in a Fully-Depleted LWIR HgCdTe P-on-n Heterojunction: Analytical and Numerical Simulations

Schuster

DeWames²,

Wijewarnasuriya

2017

In this paper, we use the theory of Evans and Landsberg, which is a generalization of the Shockley-Read-Hall recombination statistics in the space charge region (SCR), to include effects of Auger and radiative recombination processes that are also of origin in the SCR. Using analytical expressions for the current density, we calculate the total dark current density for a variety of conditions. Contributions include radiative and Auger transitions of origin in both the quasi-neutral region and the SCR. Numerical simulations are used to assess the nature of the limitations associated with the analytical calculation in the n-extrinsic region (N d ) n i , where N d is the doping concentration and n i is the intrinsic carrier concentration), and to extend the calculations to operating temperatures in the intrinsic region (n i ) N d ). Major findings include the observation that in a fully depleted P þ n doublelayer planar hetero-structure, at a reverse bias voltage sufficiently high to suppress the Auger process, SRH centers are not limiting, and the dark current is due to radiative transitions of origin in the n-side SCR. From the numerical simulations, while the Auger recombination rate changes drastically with varying the carrier concentration (such as applying reverse bias), the radiative recombination rate remains nearly invariant to varying the carrier concentration, and, as such, does not appreciably change with increasing reverse bias. Using the theory of van Roosbroeck and Shockley, the radiative recombination rate is obtained by integrating the measured optical absorption coefficient over all photon energies. Hence, the theory links the measured absorption coefficient to the measured dark current density for conditions in which the dominant current component is due to radiative recombination. Finally, the numerical simulations reveal, in both the n-extrinsic and intrinsic operating regions, that, under sufficient conditions, the detector is radiatively limited.