|About this Abstract
||2010 Electronic Materials Conference
||TMS 2010 Electronic Materials Conference
||X4, Investigation of Antimonide Infrared Detectors Based on the nBn Design
||Stephen Myers, Arezou Khoshakhlagh, Elena Plis, Maya Kutty, Ha Sul Kim, Nutan Gautam, Brianna Klein, Ralph Dawson, Sanjay Krishna
|On-Site Speaker (Planned)
Infrared detectors are important tools with many wide ranging applications including defense, security, astronomy and medical diagnostics. The applications of infrared detectors are however limited by expensive and bulky cooling systems which are required for them to operate properly. The development of heterostructure designs capable of increasing operating temperature and reducing dark current density has thus become very important. Recently uni-polar designs utilizing barrier regions have gained much interest for achieving these characteristics. The nBn structure as developed by Maimon and Wicks utilizes an n-type contact region “n”, a barrier region “B” with a large conduction band offset but no offset in the valence band, and a n-type absorber region. The large conduction band offset blocks electrons while allowing minority carriers to flow unimpeded. This design reduces dark current associated with generation-recombination (G-R) by alleviating the presence of a depletion region, as in the case of a p-i-n photodiode, making the detector diffusion limited at all temperatures. Another advantage that can be utilized with the nBn design is the suppression of surface leakage current which is a significant challenge of state of the art p-i-n designs, by utilization of shallow etching. In a typical p-i-n device, one pixel is distinguished from neighboring pixels by mesa isolation etching, however, with nBn shallow etching a pixel is distinguished from neighboring pixels by the minority carrier diffusion length. In order to fully capitalize on this design the different regions need to be optimized in terms of composition and doping level. The doping level is important because it dictates the offset of the bandstructure between the different regions. Previously, a study was conducted that investigated different doping levels of the absorber region of an InAs/GaSb superlattice nBn detector which revealed that careful tuning of the absorber doping level can improve device characteristics in terms of dark current density and detectivity. The barrier is a key component of the nBn design since it controls the flow of majority and minority carriers. It must be thick enough to prevent tunneling of majority carriers (electrons) and high enough to avoid thermal excitation in the conduction band. The doping level in the barrier region affects the valence band offset which impacts the behavior of the minority carriers (holes) consequently influencing the total dark and photo current of the detector. In this presentation a detailed study of the barrier region composition and doping level will be analyzed along with their impact on the device performance.