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

高频直接调制垂直腔面发射激光器（VCSEL）和密集的VCSEL阵列有望改变整个近距离互连的模式。用光子代替电子有望显著增加带宽并降低从硅IC I/O到模块和板级互连的功率。量子点（QDs）由于其离散的电子谱，具有优于量子阱的基本优势，有利于激光二极管的性能特性。该提案解决了量子点均匀和非均匀电子谱的纳米工程，以实现适合用于高速vcsel的短距离（低至片外I/O）光互连的增益介质的性能。该器件的主要目标性能特征包括直接调制带宽40 GHz，低功耗工作几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)开发与mbe相关的纳米工程方法，以控制自组装InAs多层量子点的尺寸、密度、形状以及最终的电子光谱和瞬态现象；提供量子点的最小分散尺寸；为形状工程提供了增加波函数重叠积分和加速激光态弛豫动力学的手段；减少网点上载流子的蒸发。（ii） QD介质带结构工程与高速VCSEL结构实现，提高微腔q因子；通过应用谐振隧道结直接注入量子点基态，减少量子点基态（激光）的弛豫时间；减小串联电阻和寄生电容。工作计划包括量子点激光异质结构的理论分析和仿真；利用生长动力学控制、能带结构和形状工程以及掺杂技术开发具有高增益、快速捕获和弛豫时间的QD活性介质；边缘发射激光二极管增益介质的测试隧道注入异质结VCSELs的设计与实现；利用原位RHEED、非原位SEM、SPM、fib -横截面、分析TEM、光致发光、直流和微波等方法对QD结构和测试器件进行了系统的表征和测试。

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.