Dual-carrier multiplication high-gain MWIR strain layer superlattice impact ionization engineered avalanche photodiodes

A novel heterostructured dual carrier multiplication extremely high gain MWIR InAs/InGaSb Type II strained layer superlattice (T2SLS) impact ionization engineered (I2E) APD was designed and simulated. Spatially separated T2SLS electron and hole multiplication regions are designed using 14 band k.p bandstructure modeling. In the novel dual carrier device, the I2E T2SLS electron and hole multiplication regions are placed right next to each other. This allows for a carrier feedback between the electron and hole multiplication regions. This feedback between the electron and hole multiplication regions allows for extremely high gain values for the overall device. While the individual gain of the electron and hole multiplication regions can be kept extremely low, the overall gain can be >103. This can be achieved at a reverse bias of 3.5V. The effective k is designed to be approximately .07. Such low bias operation of the MWIR APD allows for active operation and passive mode operation on the same pixel using standard ROIC and this opens up possibility of large format dual mode imaging arrays.