Generation-Recombination Effect in High-Temperature HgCdTe Heterostructure Nonequilibrium Photodiodes

Abstract

The dark current of near-room-temperature long-wavelength heterojunction photodiodes was studied. The dark current of the devices is much greater than that calculated from the Auger generation mechanisms. A model of trapassisted tunneling via traps located at dislocation cores is proposed as the mechanism of enhanced thermal generation of charge carriers in reversebiased diodes. Field-induced reduction of trap activation energies can increase thermal generation and create conditions for tunneling currents. The model qualitatively explains experimental currentÀvoltage characteristics of the diodes assuming a dislocation density of approximately 10 8 cm À2 at the graded gap interface between absorber and contact regions of the photodiode.

High frequency response of near-room temperature LWIR HgCdTe heterostructure photodiodes

“…(1)- (4) [12]. This method has been used for modelling many optoelectronic device structures [13][14][15][16][17]. A new factor connected with dislocations has been widely presented in Ref.…”

Enhanced numerical analysis of current-voltage characteristics of long wavelength infrared p-on-n HgCdTe photodiodes

“…(3)- (6). This method has been used for modelling many optoelectronic device structures [10][11][12][13][14][15][16][17].…”

“…(7) includes Auger 1 and Auger 7, radiative and Shockley-Read-Hall (SRH) mechanisms. Including band-to-band tunnelling and impact ionization as the generation-recombination processes, G BTB and G ION , the thermal generation rate can be expressed as [15][16][17]:…”

Analysis of current voltage characteristics of MWIR homojunction photodiodes for uncooled operation

“…Various novel concepts have been proposed to improve performance of uncooled detectors such as proper selection of semiconductor material based on the ratio of absorption coefficient (a) to thermal generation rate (G), increase of optical collection to geometrical area ratio by optical immersion [1] and use of advanced device architectures such as stacked multijunction cells [1,2]. However, most of the reported device designs for near room temperature operation are based on heterojunction configuration which requires the complex growth process of multiple layers by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD) [3]. The expected gain in dark current in heterojunction devices may be slightly lost due to loss in photosignal or quantum efficiency (QE) due to the presence of barrier particularly so in the non equilibrium mode heterojunction devices.…”

“…Though these processes limit the device performance at or near room temperatures, one must also consider the effect of tunneling and surface leakage currents on dark current of uncooled devices. Surface leakage currents and tunneling effects arise from accumulated or depleted passivant/HgCdTe interface and due to defects and dislocations that thread through the HgCdTe material either near the junction in bulk or near the surface [3,7]. More recently, higher dark current in real devices has been attributed to increased thermal generation recombination currents at dislocations located at heterojunction interfaces and contacts of the photodiodes [3].…”