半导体/超晶格分布布拉格反射镜的特性研究

Characteristics of Semiconductor/Superlattice Distributed Bragg Reflector

在n+ GaAs (10 0 )衬底上由分子束外延技术 (MBE)生长了以 [GaAs/AlAs]超晶格替代AlxGa1-xAs所形成的新型AlAs/ [GaAs/AlAs]半导体 /超晶格分布布拉格反射镜 (DBR) ,并对此DBR的光、电学特性进行了实验测量。从实验获得的DBR的反射谱中得出 ,其反射谱中心波长为 85 0nm ,19周期此DBR的峰值反射率高达 99 5 % ,反射带宽度为 90nm左右。与此同时 ,由自行设计的二次钨丝掩模质子注入形成 15× 15 μm2 正方形电流注入区对 p型DBR的串联电阻进行了测量 ,克服了化学湿腐蚀法中腐蚀深度不易控制及侧面同时被腐蚀的缺点。实验得出此 p型DBR的串联电阻仅为 5 0Ω左右。由此可见 ,此DBR在保持高的反射率的同时具有较低的串联电阻。最后 ,对DBR的串联电阻与温度关系的实验研究表明 ,此DBR的串联电阻受温度的影响不大。

By replacing the Al x Ga 1- x As with superlattice, a novel semiconductor/superlattice distributed Bragg reflector has been grown by molecular beam epitaxy system, at the same time the optical and electrical characteristics have also been measured. From the experimental results the center wavelength of the DBR reflection spectrum is about 850nm, the 19 period DBR has the reflectivity as high as 99 5%, and the reflection bandwidth is as wide as 90nm. Moreover, using twice self designed tungsten filament mask and proton implantation method we made the 15×15μm 2 square current flowing area to measure the series resistance of the p type DBR. This method avoided the difficulty in controlling the depth of implantation, and prevented the occurrence of side etching in wet chemical etching. The series resistance of the p type DBR is just about 50 Ohms. Therefore this kind of DBR has both a high reflectivity and low series resistance. Comparing with the normal semiconductor/semiconductor DBR, this kind of DBR can also simplify the structure design and fabrication of DBRs by omitting the modified heterointerface structures in the former DBR. It is clear that the simplification of the structure of DBRs can be a serious advantage in the VCSELs structure, therefore these factors reveal that this kind of DBR may have sufficient quality for the characteristics of VCSELs or the fabrication of the devices. Finally, the dependence of the series resistance of the DBR on temperature is also experimentally studied, from the result the series resistance depends on temperature slightly. It is clear that the thermal current depends more on temperature than the tunneling current, so the tunneling current should account for the majority of the current flowing in this kind of DBR, and it makes the DBR depend on temperature slightly. In VCSELs, the temperature characteristic is an important point in the performances of devices, so the characteristic of resistance depending on temperature slightly in this kind of DBR may improve the temperature characteristics of VCSELs with this kinds of DBRs.