New Avalanche Photodiodes for Fiberoptics Applications

在光纤通信系统中，探测器是主要组成部分之一。目前，Ge和GaInAs p-i-n以及雪崩光电二极管（APD）是该应用的主要探测器。然而，具有与Si APD相当的雪崩增益和噪声系数的APD仍然不可用。HgCdTe具有可控的低掺杂、50以上的高倍增增益和高k值（8-12，而Ge和GaInAs的k值为0.3-2），是制造高性能APD的潜在材料之一。该项目的第一阶段研究了采用液相外延（LPE）和金属有机化学气相沉积（MOCVD）方法生产常规APD和阶梯APD的可行性。结果，特别是LPE生产的常规APD，超出了项目预期。这些APD的性能不仅远好于最近报道的用其他方法制备的HgCdTe APD，而且与报道的Ge和GaInAs APD相当或更好。然而，在HgCdTe APD投入商业应用之前，还需要解决一些潜在的问题。因此，在本二期项目中，提出解决这些问题，并生产出高质量的HgCdTe APD原型用于商业应用。具体目标包括：(1)实现低串联电阻；(2)可靠性测试；(3)增加窗层带隙；(4)形成保护环结构；(5)分析其他器件结构。本研究解决了将光束信息转换为可用电信号的问题。这种转换是光波通信系统的核心。这不仅是重要的，以良好的效率，但也必须以尽可能少的噪音完成。这项特殊的研究将利用一种特殊材料的已证明的特性，使这种电转换器或“探测器”具有优于其他材料的特性。

In fiberoptics communication systems, detectors are one of the major components. Currently, Ge and GaInAs p-i-n and avalanche photodiodes (APD) are the major detectors for this application. However, an APD with comparable avalanche gain and noise figure to a Si APD is still not available. HgCdTe, because of its controllable low doping, high multiplication gain of over 50, and a high k value (8-12 in contrast of 0.3-2 for Ge and GaInAs), is potentially one of the promising materials for making high performance APD. Phase I of this program investigated the feasibility of using liquid phase epitaxy (LPE) and metal-organic chemical vapor deposition (MOCVD) methods to produce conventional APD and staircase APD. The results, especially the conventional APD produced by LPE, exceeded the program expectation. The characteristics of these APD are not only much better than those recently reported on HgCdTe APD made by other methods, but are also comparable or better than those reported on Ge and GaInAs APD. However, before the HgCdTe APD is used commercially, a number of potential problems have to be solved. Therefore, in this Phase II program, it is proposed to solve these problems and to produce a prototype high quality HgCdTe APD for commercial application. The specific goals include (1) Achieving a low series resistance, (2) Reliability test, (3) Increasing the bandgap of the window layer, (4) Forming a guard ring structure, and (5) Analyzing other device structures. This research addresses the conversion of light beam information into useable electrical signals. This conversion is central to lightwave communication systems. Not only is it important to do this with good efficiency, but it must also be done with as little noise as it possible. This particular research will exploit the demonstrated characteristics of a particular material in which to make such electrical convertors or "detectors" with characteristics superior to those available from other materials.