High-speed Low Noise Short-wavelength Infrared Type 2 Superlattice Heterojunction Phototransistors

(To date, most optical receiver designs have employed pin photodiodes as photodetectors. However, these devices exhibit no internal/intrinsic gain, and the increased capacitance due to their relatively large-area intrinsic absorption layer is known to be the limiting factor for high frequency operation of the photoreceiver. Heterojunction phototransistors (HPTs) are an alternative technology that can demonstrate both high speed and internal gain. Functionally, a HPT is a pin photodiode integrated with a bipolar transistor to form an integrated amplifier. Unlike avalanche photodiodes (APDs), HPTs can provide large photocurrent gain without requiring high bias voltages or the excess avalanche noise characteristic of avalanche photodiode operation. Furthermore, HPTs are well suited to integration with heterojunction bipolar transistors in receivers or other circuits. It is, therefore, expected that HPTs will provide an exciting alternative for the manufacture of optical receivers and high-sensitivity imagers at wavelengths longer than 1.55 m. A type-II superlattice (T2SL) material system and design can be a promising alternative for HPT SWIR devices. T2SLs are a developing material system that has led to the development of high performance HPTs. The T2SL-based HPTs can also be a possible solution to the urgent demand for sensitive and high speed photodetectors. In this project, the temperature dependence performance of SWIR T2SLs-based HPT device for different size have been investigated and demonstrated for the first time in the world. The novel device structure, worlds first SWIR resonant cavity enhanced heterojunction phototransistor based on type-II superlattices grown by MBE has been demonstrated. The high performance MWIR HPT devices based on T2SLs have also been developed for the first time in the world. We also demonstrated the design, growth, and characterization of the worlds first high-gain band-structure-engineered LWIR heterojunction phototransistor.