Optical: Nanoengineering of InAs Quantum Dot Medium for High Speed Vertical Cavity Lasers

0334994Oktyabrsky高频直接调制垂直腔面发射激光器(VCSEL)和密集VCSEL阵列有望改变短距离互连的整个范式。用光子取代电子有望极大地增加带宽，降低互连的功率，范围从硅IC I/O到模块和板级。量子点由于其离散的电子光谱，与量子阱相比具有根本的优势，这将有利于激光二极管的性能特性。该方案解决了量子点的均匀和非均匀电子光谱的纳米工程，以实现适合用于短距离(下至芯片外I/O)光学互连的高速VCSEL的增益介质的性能。该器件的主要目标性能特征包括直接调制带宽40 GHz，低功率工作几mW，工作温度高达100℃，这是与硅芯片直接集成所必需的。该方法包括：(I)发展与分子束外延相关的纳米工程方法，以控制自组装的InAs多层量子点的尺寸、密度、形状以及最终的电子光谱和暂态现象；提供最小尺寸的量子点的弥散；为形状工程提供手段，以增加波函数重叠积分，并加速弛豫动力学到激光状态；减少载流子从点的蒸发。(Ii)QD介质的能带结构设计和高速VCSEL结构的实现，以提高微腔Q因子；通过应用共振隧道结直接注入到QD基态来缩短到QD基态(激光)的驰豫时间；减少串联电阻和寄生电容。工作计划包括：量子点激光异质结的理论分析和模拟；利用生长动力学、能带结构和形状工程以及掺杂的控制，开发具有高增益和快速俘获和驰豫时间的量子点有源介质；测试边缘发射激光二极管的增益介质；设计和实现隧道注入异质结垂直腔面发射激光器；利用原位RHEED，以及非原位扫描电子显微镜、扫描电子显微镜、FIB横截面、分析电子显微镜、光致发光、电直流和微波等方法对量子点结构和测试器件进行系统的表征和测试。

0334994OktyabrskyHigh-frequency directly modulated Vertical Cavity Surface Emitting Lasers (VCSELs) and dense VCSEL arrays are expected to change the whole paradigm of short-range interconnections. Substitution of electrons with photons is expected to dramatically increase bandwidth and reduce power of interconnects ranging from silicon IC I/O's to module- and board-level. Quantum Dots (QDs) due to their discrete electronic spectrum have fundamental advantages over quantum wells that could benefit performance characteristics of laser diodes. The proposal addresses nanoengineering of both homogeneous and inhomogeneous electronic spectra of quantum dots to achieve the performance of the gain medium suitable for utilization in high-speed VCSELs for short range (down to off-chip I/O) optical interconnects. The major target performance characteristics of the device include direct modulation bandwidth 40 GHz, low-power operation of a few mW, and operation temperatures up to 100 0C, necessary for direct integration with a Si chip. The approach involves: (i) development of MBE-related nanoengineering methods to control size, density, shape, and ultimately electronic spectrum and transient phenomena in self-assembled InAs multilayer QDs; to provide minimum size dispersion of the QDs; give the means for shape engineering to increase wave function overlap integral and accelerate the relaxation dynamics to the lasing state; reduce evaporation of carriers from the dots. (ii) Band-structure engineering and implementation of high speed VCSEL structure for QD medium to increase microcavity Q-factor; reduce relaxation time onto the QD ground (lasing) states via application of resonant tunnel junction for direct injection into the QD ground state; reduce series resistance and parasitic capacitance. The work plan includes theoretical analysis and simulation of the QD laser heterostructures; development of QD active medium with high gain and fast capture and relaxation times using control of growth kinetics, band-structure and shape engineering, and doping; testing of the gain medium in edge-emitting laser diodes; design and implementation of VCSELs with tunnel injection heterojunctions; systematic characterization and testing of the QD structures and test devices using in-situ RHEED, and ex-situ SEM, SPM, FIB-cross sectioning, analytical TEM, photoluminescence, electrical DC and microwave methods.