Vertical Cavity Blue and Ultraviolet Light Emitters

在这个项目中，Nurmikko、他的研究生和合作者致力于研究、设计和开发光电子器件和光学物理概念，以实现基于宽带隙氮化物半导体异质结的蓝光和紫外光垂直腔光发射器。特别是，三年计划的具体目标是示范和制造(A)谐振腔发光二极管(RCLED)和(B)垂直腔面发射激光器(VCSEL)。尽管紧密相连，但这些新的、紧凑的短波长器件的开发所面临的技术挑战可以从逻辑上分为两个大的领域：(I)光学微谐振器结构的方法和实现；(Ii)基于pn结的注入器结构的设计和实现。为了实现InGaN和AlGaN异质结的高Q因子垂直腔体，Nurmikko和他的同事们的目标是创造加工技术，使光学结构达到1000-2000范围内的Q因子，从而降低对激光阈值的要求。该方法基于两个介质DBR的单片集成，也关注具有一个介质和一个生长的DBR的“混合”结构。VCSEL结构的光学增益谱的研究形成了另一个关键的项目领域，详细地描述了InGaN和AlGaN有源介质的增益谱，从而优化了低阈值VCSEL的这些增益谱。Nurmikko和他的同事将研究基本的微腔物理，以增强InGaN和AlGaN VCSELs和RCLEDS的光发射。激子对振子强度的增强可以集中光增益，从而显著降低氮化物VCSEL阈值。为了实现二极管垂直腔体发射器，Nurmikko和他的同事将通过两种类型的实验来研究横向p注入：(I)使用近场成像技术来研究横向扩散，以及(Ii)LED微结构的设计，其中电流扩散可以通过电致发光空间成像获得。对于BLUE和NUV VCSEL的工作，他们还将致力于掺入p-GaN/AlGaN调制掺杂异质结以提高p侧的电导率。它们将解决的具体特征之一涉及到电子结构的定制，以便可以减少界面散射(从而提高空穴迁移率)。他们建议使用非常大的内置压电和自发介电极化效应来静电设计异质结限制轮廓。他们还将研究外延横向外延生长(ELOG)的使用，以促进“埋藏式”DBR反射镜的结合，并定义通向有源器件区域的沟道空穴传输的电流孔径(由垂直谐振器定义)。正在进行的研究的一个具体特征是与惠普(HP Labs和光电部门，现已更名为Agilent Technologies)以及桑迪亚国家实验室的密切合作。这一行业/政府实验室连接将是项目工作的组成部分。*

0070887NurmikkoIn this project, Nurmikko, his graduate students, and collaborators aim to study, design, and develop optoelectronic device and optical physics concepts that will lead to the realization of blue and ultraviolet vertical cavity light emitters, based on wide band gap nitride semiconductor heterostructures. In particular, the specific goals of the three year program are the demonstration and fabrication of (a) a resonant cavity light emitting diode (RCLED), and (b) a vertical cavity surface emitting laser (VCSEL). Although closely interconnected, the technical challenges facing the development of these new, compact short wavelength devices can be logistically grouped into into two broad areas: (i) the approach and implementation of the optical microresonator structure and (ii) the design and realization of a pn-junction based injector structure. To achieve high Q-factor vertical cavities for InGaN and AlGaN heterostructures, Nurmikko and co-workers aim is to create processing techniques that will create optical structures reaching Q-factors in the 1000-2000 range for reducing the laser threshold requirements. The approach is based on monolithic integration of two dielectric DBRs and also focus on "hybrid" structures with one dielectric and one as-grown DBR. Study of the optical gain spectra of the VCSEL structures forms another key project area, to detail the gain spectra of the InGaN and AlGaN active media for optimizing these for low threshold VCSELS. Nurmikko and co-workers will study fundamental microcavity physics to enhance light emission from InGaN and AlGaN VCSELs and RCLEDS. Excitonic enhancement to oscillator strength can concentrate optical gain so as to significantly reduce a nitride VCSEL threshold. Similarly, spontaneous emission properties for an RCLED are expected to be dramatically enhanced.For achieving a diode vertical cavity emitter, Nurmikko and co-workers will study lateral p-injection in two types of experiments: (i) the use of near field imaging techniques to study lateral diffusion, and (ii) the design of LED microstructures where current spreading can be obtained from electroluminescence spatial imaging. For the blue and NUV VCSEL work they will also concentrate on the incorporation of p-GaN/AlGaN modulation doped heterostructures for enhancing the p-side conductivity. One of the specific features that they will address concerns the tailoring of the electronic structure so that interface scattering can be reduced (hence the hole mobility enhanced). They propose to use the very large built-in piezoelectric and spontaneous dielectric polarization effects to electrostatically design the heterojunction confinement profile. They will also study the use of epitaxial lateral overgrowth (ELOG) to facilitate both the incorporation of "buried" DBR mirrors as well as to define current apertures for channeling hole transport to the active device region (as defined by the vertical resonator).A specific characteristic of the ongoing research is a close collaboration with Hewlett-Packard (both HP Labs and the Optoelectronic Division, now renamed Agilent Technologies), as well as Sandia National Laboratories. This industry/government laboratory connection will be an integral part of the project work.***