F. Yin

Analysis of temperature dependence of dark current mechanisms for long-wavelength HgCdTe photovoltaic infrared detectors

Resistance-voltage curves of n-on-p Hg1−хCdxTe long-wavelength infrared photodiodes forming 128-element array are measured in the temperature range of 40–150 K. Experimentally obtained characteristics are fitted by the simultaneous-mode nonlinear fitting program. The dark current mechanisms induced by diffusion, generation recombination, trap-assisted tunneling, band-to-band tunneling, and series resistance effect are included in the physical model for R-V curve fitting. Six characteristic parameters as function of temperature are extracted from measured R-V curves. The characteristics of extracted current components at low temperatures indicate significant contributions from tunneling effects, which is the dominant leakage current mechanism for reverse bias greater than approximately 50 mV. The Hg-vacancy-induced acceptor trap tends to invert to donor type at higher temperature, typically larger than 120 K, while it can maintain stable at the temperature of 60–40 K. The stable temperature of ion-implanta...

Two-dimensional transient simulations of drain lag and current collapse in GaN-based high-electron-mobility transistors

The intrinsic mechanisms of drain lag and current collapse in GaN-based high-electron-mobility transistors are studied by using two-dimensional numerical simulations. Simulated drain lag characteristics are in good agreement with reported experimental data. The dynamic pictures of trapping of hot electrons under drain-pulse voltages are discussed in detail. Hot-electron buffer-trapping effect plays an instrumental role in the current collapse mechanism. Polarization-induced interface charges have significant effect on the hot-electron buffer trapping and the current collapse can be weakened by increasing the interface charges. The trapped charges can accumulate at the drain-side gate edge, where the electric field significantly changes and gate-to-drain-voltage-dependent strain is induced, causing a notable current collapse. The simulation results show that the drain voltage range, beyond 5 V, is already in the field of the well-developed hot electron regime. The hot electrons can occupy a great number of...

Dependence of Ion-Implant-Induced LBIC Novel Characteristic on Excitation Intensity for Long-Wavelength HgCdTe-Based Photovoltaic Infrared Detector Pixel Arrays

In this paper, experimental results of laser-irradiance-dependent polarity inversion of laser beam induced current (LBIC) for As-doped long-wavelength HgCdTe pixel arrays grown on CdZnTe are reported. Models for the ion-implant-induced junction transformation are proposed, and demonstrated using numerical simulations. The novel trap-related p-n junction transformation induced by ion implantation is observed under typical laser irradiances for low temperature. The implantation-induced traps and Hg interstitial diffusion are key factors for inducing the LBIC coupling, polarity reversion, and junction broadening at different laser irradiances. The trap type, trap density, and junction configuration are extracted from the measured experiment data. The results provide the near room-temperature HgCdTe photovoltaic detector with a reliable reference on the junction reversion and broadening around implanted regions, as well as controlling the n-on-p junction formation for very long wavelength HgCdTe infrared detector pixels.

Polarity inversion and coupling of laser beam induced current in As-doped long-wavelength HgCdTe infrared detector pixel arrays: Experiment and simulation

In this paper, experimental results of polarity inversion and coupling of laser beam induced current for As-doped long-wavelength HgCdTe pixel arrays grown on CdZnTe are reported. Models for the p-n junction transformation are proposed and demonstrated using numerical simulations. Simulation results are shown to be in agreement with the experimental results. It is found that the deep traps induced by ion implantation are very sensitive to temperature, resulting in a decrease of the quasi Fermi level in the implantation region in comparison to that in the Hg interstitials diffusion and As-doped regions. The Hg interstitial diffusion, As-doping amphoteric behavior, ion implantation damage traps, and the mixed conduction, are key factors for inducing the polarity reversion, coupling, and junction broadening at different temperatures. The results provide the near room-temperature HgCdTe photovoltaic detector with a reliable reference on the junction reversion and broadening around implanted regions, as well a...

Laser drilling induced electrical type inversion in vacancy-doped p-type HgCdTe

Femtosecond laser was used to generate micrometer-sized holes in vacancy-doped p type mercury cadmium telluride (HgCdTe). Characterization by laser beam induced current (LBIC) microscope shows obvious electrical type inversion around each hole. Both the intensity of the LBIC signals and the spatial dimension of the type-inversed regions are well comparable with those of n-on-p HgCdTe photodiodes formed by the conventional ion milling technique. The observation demonstrates the potential of laser drilling to be a new tool in fabricating HgCdTe photodiode arrays.

Temperature-sensitive junction transformations for mid-wavelength HgCdTe photovoltaic infrared detector arrays by laser beam induced current microscope

In this paper, we report on the disappearance of the photosensitive area extension effect and the unusual temperature dependence of junction transformation for mid-wavelength, n-on-p HgCdTe photovoltaic infrared detector arrays. The n-type region is formed by B+ ion implantation on Hg-vacancy-doped p-type HgCdTe. Junction transformations under different temperatures are visually captured by a laser beam induced current microscope. A physical model of temperature dependence on junction transformation is proposed and demonstrated by using numerical simulations. It is shown that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation dependence on temperature, and the weaker mixed conduction compared with long-wavelength HgCdTe photodiode contributes to the disappearance of the photosensitive area extension effect in mid-wavelength HgCdTe infrared detector arrays.

The role of localized junction leakage in the temperature-dependent laser-beam-induced current spectra for HgCdTe infrared focal plane array photodiodes

We have performed the study on the dependence of laser beam induced current (LBIC) spectra on the temperature for the vacancy-doped molecular beam epitaxy grown Hg1−xCdxTe (x = 0.31) photodiodes by both experiment and numerical simulations. It is found that the measured LBIC signal has different distributions for different temperature extents. The LBIC profile tends to be more asymmetric with increasing temperature below 170 K. But the LBIC profile becomes more symmetric with increasing temperature above 170 K. Based on a localized leakage model, it is indicated that the localized junction leakage can lead to asymmetric LBIC signal, in good agreement with the experimental data. The reason is that the trap-assisted tunneling current is the dominant leakage current at the cryogenic temperature below 170 K while the diffusion current component becomes dominant above the temperature of 170 K. The results are helpful for us to better clarify the mechanism of the dependence of LBIC spectra on temperature for th...

Effects of hetero-related bulk-traps on photoresponse for long-wavelength HgCdTe infrared photodiode

Effects of hetero-related bulk traps on photoresponse for long-wavelength Hg1−xCdxTe infrared photodiodes have been numerically studied. The model involves a generalized approach, taking into account absorption coefficient, trap-assisted and band-to-band tunneling recombination mechanism, and bulk traps distributions associated with misfit dislocations present in the GaAs-substrate/Hg1−xCdxTe hetero-structure. The characteristic x-dependent material parameters, used in the simulations, such as donor concentration, trap density and level, and minority lifetime, are extracted by the simultaneous-mode nonlinear fitting procedure.

Study of junction performance in mid-wavelength HgCdTe photodiodes by laser-beam-induced current microscope

This paper reports on the disappearance of photosensitive area extension effect and the novel temperature dependence of junction performance for mid-wavelength HgCdTe detectors. The performances of junction under different temperatures are characterized by laser beam induced current (LBIC) microscope. The physical mechanism of temperature dependence on junction transformation is elaborated and demonstrated using numerical simulations. It is found that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation depended on temperature, and wider band gap compared with the long-wavelength HgCdTe photodiode may correlate with the disappearance of photosensitive area extension effect.

Simulation of laser beam induced current for HgCdTe photodiodes with leakage current

We report on 2D numerical simulations of laser beam induced current (LBIC) for HgCdTe photovoltaic detector. The effect of junction leakage current on the LBIC signal is investigated, and different leakage paths caused by different reasons in HgCdTe photodiode arrays are taken into account in the simulation. The simulation results are in good agreement with the experiment data. Simulation results suggest that the LBIC can be used to determine the existence of the junction leakage current and investigate the original of the junction leakage current.