SBIR Phase I: Low-Noise AlGaSb Avalanche Photodiodes

这项小型企业创新研究（SBIR）第一阶段项目旨在研究金属有机化学气相沉积（MOCVD）外延生长，并探索极低噪声锑化铝镓（AlGaSb）雪崩光电二极管（apd）的新钝化技术。在一种特定的组成（~6% Al）下，AlGaSb的带隙和价自旋轨道分裂能变得相等，共振地提高了空穴电离率。一些研究小组已经报道了AlGaSb的高空穴电子电离比（7到20）。其他具有1.0-1.7微米响应的半导体缺乏高空穴/电子或电子/空穴电离比（InGaAs~2, e~1.5, InGaAsP~3），这对低噪声apd至关重要。例如，AlGaSb APD的过量噪声因子应为2，而Ge APD的过量噪声因子为7.5，增益为10。以前的AlGaSb apd是在10-20年前通过液相外延（LPE）制造的，存在质量和均匀性（如20%的厚度变化）问题，并且报道了不同的最佳组成。具有高纯度来源的MOCVD将用于生长更均匀（3%掺杂变化，1%厚度和成分），更高质量的脱毛膜，现在可以更好地表征。这将使精确的组成和外延结构最好地利用相当尖锐的共振增强。与PIN/反式阻抗放大器相比，1.0至1.7微米范围内的可用apd具有噪声。提出的低噪声AlGaSb apd将允许单个组件取代大部分PIN/反阻抗放大器前端，并显着扩展光通信和激光雷达系统的设计空间。

This Small Business Innovative Research (SBIR) Phase I project seeks to research the metal-organic chemical vapor deposition (MOCVD) epitaxial growth and explore new passivation techniques for very low-noise aluminum gallium antimonide (AlGaSb) avalanche photodiodes (APDs). At one particular composition (~6% Al), the AlGaSb bandgap and valence spin-orbit splitting energy become equal, resonantly enhancing the hole ionization rate. Several groups have reported high (7 to 20) hole-to-electron ionization ratios in AlGaSb. Other semiconductors with 1.0-1.7 micron response lack high hole/electron or electron/hole ionization ratios InGaAs~2, e~1.5, InGaAsP~3) crucial for low noise APDs. For example, the AlGaSb APD excess noise factor should be 2, versus 7.5 for Ge APDs at a gain of 10. Previous AlGaSb APDs were made 10-20 years ago by liquid phase epitaxy (LPE), which had quality and uniformity (e.g. 20% thickness variation) issues, and different optimal compositions were reported. MOCVD with high purity sources will be used to grow more uniform (3% doping variation, 1% for thickness and composition), higher quality epilayers that can now be better characterized. This should enable the exact composition and epi structure to best use the fairly sharp resonant enhancement.Available APDs in the 1.0 to 1.7 micron range are noisy compared with PIN/trans-impedance amplifiers. The proposed low-noise AlGaSb APDs would allow a single component to replace most of the PIN/trans-impedance amplifier front end, and significantly extend the design space in which optical communications and laser radar systems are constrained.