Minority carrier dynamics of type-II indium arsenide/gallium antimonide superlattice photodiodes via optical and electrical characterization.

摘要

Semiconductors and the devices made from them are teeming with activity at every moment and in an anthropomorphic way, and can be treated using concepts directly related to living objects. Free carriers, either electrons or holes, in semiconductors have definitive periods of existence before they are annihilated or destroy one another. Thus, the charge carries within a semiconductor material or device do not persist forever and must go from existing to not. The period of carrier existence, carrier lifetime, constitutes subjects of intensive studies worldwide because their understanding guides manipulation of device design with the motive of improving their performance.;From theory, the Type-II superlattice has many distinct features that make it an ideal material system for infrared detection, including its theoretical ability to adjust its carrier lifetime through band engineering. In comparison to the commercially available infrared detectors, the Type-II InAs/GaSb superlattice system grown on GaSb substrates is an attractive alternative because it has good spatial uniformity and the ability to tune the cut-off wavelength from 3-to-32 mum. In addition, through band engineering it is possible to modify the internal carrier lifetimes and thus achieve higher performance, since the lifetime is the fundamental limitation within any semiconductor.;In this work, the techniques to study the internal carrier dynamics of the Type-II InAs/GaSb superlattice will be discussed, as well as how the structure of the photodiode can be modified for improved performance. Through optical and electrical characterization, the current limitations that face this material system can be revealed. The use of a phase-sensitive lock-in technique, in conjunction with a Fourier transform spectrometer based photoluminescence has become routine for samples with bandgaps up to 25 mum. Studying the emission properties of the positive and negative electroluminescence lead to a deeper understanding of the recombination mechanisms within the superlattice photodiodes. By studying the novel phenomenon known as negative luminescence, internal carrier dynamics of both MWIR and LWIR superlattice photodiodes were modeled. In addition, this work demonstrated the negative luminescence phenomenon with high efficiency for MWIR diodes beyond room temperature and currently the longest negative luminescence in III-V materials. Adapting the capacitance-voltage measurement to InAs/GaSb SLS photodiodes, it has been shown that the residual background impurity concentration is measured to be below 1015 cm-3. Furthermore, by introducing the dopants into the i-region of p-i-n photodiode architecture, the contribution of the different dark current mechanisms can be varied to modify the device performance.;The information obtained from the luminescence and electrical results has shown that by changing the minority carrier type from holes to electrons, the detector performance can be significantly enhanced. Changing the minority carrier type, in addition to improving the photodiode active region thickness, has significantly improved the overall signal-to-noise ratio of the photon detectors based on the InAs/GaSb superlattice material system. Finally, by improving the overall device architecture to incorporate a well-aligned double heterojunction, the dark current was further reduced, while simultaneously improving the photo-response. This has allowed the overall device performance, as shown by the detectivity, to become background limited at higher temperatures with dark current values similar to those previously achieved only by HgCdTe. Therefore, this work will show that by gaining greater insight into the internal workings of the photodiode formed by using the antimonide-superlattice has allowed for IR detectors spanning the range from the MWIR-to-VLWIR to have significantly improved performance in comparison to previously achieved results.