Study on Novel Surface Emitting Semiconductor Laser for Optically Integrated Multi-functional Optical Devices.

传统的半导体激光器采用解理形成光腔，很难实现二维单片集成。本研究首次提出并制作了一种新型的面发射激光器--同轴横向结（CTJ）。CTJ结构的制作如下：通过反应离子刻蚀在n-GaAs/n-AlGaAs/n-GaAs DH晶片上形成柱或阱结构，其侧壁垂直于衬底。然后扩散Zn以形成平行于侧壁的pn结。在这种结构中，有源区的长度与侧壁的长度相对应，从而沿着垂直于衬底的发射方向获得较大的放大增益。我们研究了三种不同类型的CTJ族，即柱状CTJ（C-CTJ）、阱型CTJ（W-CTJ）和空穴型CTJ（H-CTJ）。在这些变型中，H-CTJ结构最适合于激光操作，因为它在光学谐振器内不包含不必要的层。利用H-CTJ样品在10 K下的电流-光输出特性和振荡光谱证实了其激光运转。阈值电流为90 mA。根据目前的数据，H-CTJ激光器的室温工作的阈值电流估计为约200 mA，反射镜的反射率为90%。为了获得较低的阈值操作，需要优化Zn扩散工艺和结构尺寸。虽然这些问题都有待解决，目前的研究表明，CTJ结构的基本属性和其上级属性的二维应用。

It is rather difficult for conventional semiconductor lasers to form 2 dimentional monolithical integration, since they use cleaving to form optical cavitys. In this study, new type of surface emitting laser named Coaxial Transverse Junction (CTJ) is proposed and fabricated for the first time. The CTJ structure is fabricated as follows; the column or well structure is formed by the reactive ion etching onto the n-GaAs/n-AlGaAs/n-GaAs DH wafer, whose side wall is perpendicular to the substrate. Then Zn is diffused to form the pn junction parallel to the side wall. In this structure the length of the active region is corresponded to that of the side wall, so that the relatively latge amplified gain is obtained along the emission direction perpendicular to the substrate.We have investigated three different types of CTJ family called Column type CTJ (C-CTJ), Well type CTJ (W-CTJ) and Hole type CTJ (H-CTJ). In these variations, H-CTJ structure is most suitable for lasing operation, since it does not contain unnecessary layer within the optical resonator. Lasing operation was confirmed by the current-light output characteristic and also the oscillation spectra using H-CTJ sample at 10K. The threshold current was 90 mA. Based on the present data, the threshold current for the room temperature operation of the H-CTJ laser was estimated to be about 200 mA with 90% reflectivity of the mirror. To obtain lower threshold operation, it is necessary to optimize Zn diffusion process and the dimension of the structure. Though these problems are left to solve, the present study shows the fundamental properties of the CTJ structure and its superior properties for 2D applications.