Single Carrier Initiated Low Excess Noise Mid-Wavelength Infrared Avalanche Photodiode using InAs-GaSb Strained Layer Su
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1076-K02-02
Single Carrier Initiated Low Excess Noise Mid-Wavelength Infrared Avalanche Photodiode using InAs-GaSb Strained Layer Superlattice Koushik Banerjee1, Shubhrangshu Mallick1, Siddhartha Ghosh1, Elena Plis2, Jean Baptiste Rodriguez2, Sanjay Krishna2, and Christoph Grein3 1 Lab for Photonics and Magnetics (ECE), University of Illinois at Chicago, Chicago, IL, 60607 2 Center for High Technology Materials (ECE), University of New Mexico, Albuquerque, NM, 87106 3 Microphysics Laboratory (Physics), University of Illinois at Chicago, Chicago, IL, 60607 ABSTRACT Mid-wavelength infrared (MWIR) avalanche photodiodes (APDs) were fabricated using Indium Arsenide- Gallium Antimonide (InAs-GaSb) based strain layer superlattice (SLS) structures. They were engineered specifically to have either electron or hole dominated ionization. The gain characteristics and the excess noise factors were measured for both devices. The electron dominated p+-n--n APD with a cut-off wavelength of 4.13 µm at 77 K had a maximum multiplication gain of 1800 measured at -20 V while that of the hole dominated n+-p-p structure with a cut-off wavelength of 4.98 µm at 77 K was 21.1 at -5 V at 77 K. Excess noise factors were measured between 1-1.2 up to a gain of 800 and between 1-1.18 up to a gain of 7 for electron and hole dominated APDs respectively. INTRODUCTION Long range military and astronomical applications need to detect, recognize and track a variety of targets under a wide range of atmospheric conditions. This becomes particularly difficult due to significant absorption of the optical signal by the atmospheric gases (carbon-dioxide, carbon-monoxide and water vapor). In addition, the scattering by the air-borne dust particle makes it even more indiscernible. As a result, at the receiver, an amplification step becomes necessary in addition to the detection stage to get the detector signal above the preamp noise level. The APDs play a very significant role by combining both stages in a single device and thus simplifying the overall receiver complexity. However, avalanching being a random process, both in terms of photon-absorption and ionization, a high frequency noise known as the excess noise is incorporated at the output signal of an APD. This noise generally increases with the gain and often limits optimal performance of the device. Naturally, an APD having an excess noise factor minimally varying with gain is of prime importance for longer wavelength infrared detection. Mercury cadmium telluride (HgCdTe) has been the standard material of choice for such research in the last five to six years [1-8]. However, InAs-GaSb based superlattices, where novel band structures can be attained with the proper choice of the composition and thickness of individual layers, have also been a prospective candidate for the APD application. They have the additional advantages of relatively easier growth [9], comparable absorption coefficient [10] and longer Auger lifetime for p-doped sample [11-12], potentially resulting in an enhanced detectivity (D*) [1
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