Shubhrangshu Mallick

Ultralow noise midwave infrared InAs-GaSb strain layer superlattice avalanche photodiode

Eye-safe midwavelength infrared InAs–GaSb strain layer superlattice p+-n−-n homojunction avalanche photodiodes (APDs) grown by solid source molecular beam epitaxy were fabricated and characterized. Maximum multiplication gain of 1800 was measured at −20V at 77K. Excess noise factors between 0.8 and 1.2 were measured up to gain of 300. Gain of 200 was measured at 120K. Exponential nature of the gain as a function of reverse bias along with low excess noise factor at higher gain confirms single carrier electron-only impact ionization in the avalanche regime. Decrease in the multiplication gain at higher temperatures correlates with standard APD characteristics.

Midwave infrared InAs/GaSb strained layer superlattice hole avalanche photodiode

Midwavelength infrared InAs–GaSb strained layer superlattice n+-n−-p avalanche photodiodes, specifically designed to have hole dominated avalanching, with a zero percent cutoff wavelength of ∼6.3 μm are fabricated and characterized. Maximum multiplication gain of 105 is measured at −3.6 V at 77 K. Measured excess noise factors are significantly improved compared to unity hole to electron ionization ratio and corresponds to a theoretical value between 40 and 50 when compared with the McIntyre model. Exponential nature of the gain as a function of reverse bias along with low excess noise factors confirms single carrier hole dominated impact ionization.

Hg1-xCdxTe Mid-Wavelength Infrared (MWIR) Avalanche Photodiode (APD) Grown on Si Substrate

Photodetectors with high bandwidth and internal gain are required to detect highly attenuated optical signals for defense application and long distance communication. IR avalanche photodiodes (APDs) are best suited for this purpose due to their internal gain-bandwidth characteristics coupled with long range data transmission capability. For the past two decades, HgCdTe has been the most successful material for infrared photodetector applications. Recent advances in epitaxial growth techniques made possible the growth of advanced HgCdTe APD structures, but to the best of our knowledge all are grown on expensive substrates (e.g. CdZnTe, CdTe). We report for the first time HgCdTe-based MWIR (4.5 μm) p-i-n APD grown on Si substrate by molecular beam epitaxy (MBE). The devices were fabricated by 365nm UV photolithography and wet-etching technique. The diode had a junction area of 300μm diameter. The R0A of the diode was 3 x 106 Ω-cm2 at 77K. Multiplication gains of 800 were measured at a reverse bias of 10 V in the linear operation regime. The gain increased exponentially as the reverse bias was increased, indicating that only one carrier is responsible for the impact ionization. Temperature dependence of the multiplication gain and of the breakdown voltage further confirms that avalanche multiplication dominates high reverse bias I-V characteristics.

Hole initiated mid wave infrared InAs/GaSb strained layer superlattice avalanche photodiode

This work focuses on the performance of a MWIR hole dominated APD. The superlattice (InAs/GaAs/GaInSb/AlSb/GaAs) was specifically designed to have hole dominated avalanching.

Optimization of Surface preparation and Surface Passivant for the InAs/GaSb Strain Layer Superlattice (SLS) for Mid-wavelength Infrared (MWIR) Photodetectors

This article addresses the problems encountered during surface preparation and surface passivation of the InAs-GaSb strain layer superlattice. An analysis of the surface preparation techniques along with the effect on the performance characteristics for different passivants is presented. The passivants and surface preparation techniques are compared on the basis of their insulation properties, capacitance-voltage (C-V) characteristics, minority carrier lifetime, and 1/f flicker noise characteristics.