Extrinsic Base Surface Passivation in High Speed ＂Type-II＂ GaAsSb/InP DHBTs Using an InGaAsP Ledge Structure

Type-II GaAsSb/InP DHBTs with selectively-etched InGaAsP ledge structures are fabricated and characterized for the first time. The novel InGaAsP/GaAsSb/InP DHBTs with a 20nm lattice-matched GaAsSb base and a 75 nm InP collector have a dc current gain improvement by a factor of 2 and a cutoff frequency fT of 190 GHz. The InGaAsP ledge design provides a simple but effective approach to suppress the extrinsic base surface recombination and enable GaAsSb/InP DHBTs to further increase the operating frequencies and integration levels for millimeter wave applications.     

一种InP双异质结双极晶体管小信号物理模型及其提取方法

研究了InP双异质结双极晶体管（DHBT）的能带结构对集电极电容的影响,解决了传统方法不能准确提取InP DHBT集电极电容的问题.考虑了基极-发射极和集电极-发射极引线间的交叠电容,并从物理上区分了InP DHBT的本征电阻、外部电阻与寄生电阻,建立了一个基于物理的InP基DHBT小信号模型.同时提出了一套直接提取模型参数的方法,该方法无需引入数学优化,具有清晰的物理意义.提取的结果在很宽的偏置范围内准确地拟合了器件特性,验证了模型的准确性与提取方法的有效性. 关键词： InP双异质结双极晶体管 集电极电容 小信号模型 参数提取     

高功率转换效率905 nm垂直腔面发射激光器的设计与制备

通过对影响垂直腔面发射激光器(vertical cavity surface emitting laser, VCSEL)的功率转换效率的因素进行理论分析,得出斜率效率是影响功率转换效率的主要因素的结论.为获得高功率转换效率,通过对有源区量子阱、P型和N型分布布拉格反射镜(DBR)等进行优化,设计出了905 nm VCSEL的外延结构并进行了高质量外延生长.成功制备出了不同氧化孔径的905 nm VCSEL器件,获得的最大斜率效率为1.12 W/A,最大转换效率为44.8%.此外,探究了氧化孔径对VCSEL的远场和光谱特性的影响.这种具有高功率转换效率的905 nm VCSEL器件为激光雷达的小型化、低成本化提供了良好的基础数据.     

Beam Steering Analysis in Optically Phased Vertical Cavity Surface Emitting Laser Array

Beam steering in implant defined coherently coupled vertical cavity surface emitting laser(VCSEL) arrays is simulated using the FDTD solution software. Angular deflection dependent on relative phase differences among elements, inter-element spacing, element size and emitted wavelength is analyzed detailedly and systematically.We design and fabricate 1×2 implant defined VCSEL arrays for optimum beam steering performance. Electronically controlled beam steering with a maximum deflection angle of 1.6° is successfully achieved in the 1×2 VCSEL arrays. The percentage of the power in the central lobe is above 39% when steering. The results show that the steering is controllable. Compared with other beam steering methods, the fabrication process is simple and of low cost.     

高功率密度多结级联905 nm垂直腔面发射激光器

本文针对激光雷达等三维传感应用,设计并制备了905 nm波长的高功率密度5结级联垂直腔面发射激光器(vertical cavity surface emitting laser, VCSEL).制备的5结级联VCSEL单管(氧化孔径8μm)的功率转换效率高达55.2%;其最大斜率效率为5.4 W/A,约为相同孔径单结VCSEL的5倍.窄脉冲条件下(脉冲宽度为5.4 ns,占空比0.019%), 5结级联19单元VCSEL阵列(单元孔径20μm)的峰值输出功率达到58.3 W,对应的峰值功率密度高达1.62 kW/mm².对不同孔径器件(8—20μm)的光电特性进行了测试和分析.结果显示,这些器件的最大斜率效率均大于5.4 W/A,最大功率转换效率均大于54%.这些高性能VCSEL器件可作为激光雷达等三维传感应用的理想光源.