为提高InP基光探测器的吸收效率和工作速度，设计了一种渐变耦合脊波导单载流子传输异质结光敏晶体管探测器。采用有效折射率法和光束传播法，分析渐变耦合脊波导的光传输模式，优化后波导宽度和波导长度分别为2.6 μm和250 μm，可实现单模传输和高的光吸收效率.由于渐变耦合脊波导单载流子传输异质结光敏晶体管光传输方向与载流子运动方向垂直，分别优化光敏晶体管的吸收效率和速度，器件输出光电流和特征频率均得到改善.渐变耦合脊波导单载流子传输异质结光敏晶体管的响应度为33.83 A/W，饱和输出光电流为90 mA，最高特征频率达到87 GHz，其饱和输出电流和特征频率相比于台面单载流子传输异质结光敏晶体管分别提高了20%和24%.但渐变耦合脊波导单载流子传输异质结光敏晶体管吸收体积大，获得饱和电流时的光功率也比较大，因此渐变耦合脊波导单载流子传输异质结光敏晶体管的响应度略小于台面的单载流子传输异质结光敏晶体管的响应度.

To improve the responsivity and working speed of an InP-based optical detector, an uni-traveling carrier heterojunction phototransistor with gradual coupled ridge waveguide is designed. The optical transmission mode of the gradual coupled ridge waveguide is analyzed through effective index method and beam propagation method, and the waveguide width and length are optimized as 2.6 μm and 250 μm respectively to achieve single mode transmission and high absorption efficiency. Because the direction of optical transmission is perpendicular to the direction of carrier motion, the absorption efficiency and speed of the phototransistor are optimized, and the output photocurrent and characteristic frequency of the device are improved. The responsivity is 33.83 A/W, the saturation output photocurrent reaches 90 mA and the highest characteristic frequency is 87 GHz. Compared to the vertical-illuminated uni-traveling carrier heterojunction phototransistor, the saturated output current and characteristic frequency of the uni-traveling carrier heterojunction phototransistor with gradual coupled ridge waveguide are increased by 20% and 24% respectively. However, the uni-traveling carrier heterojunction phototransistor with gradual coupled ridge waveguide has a bigger absorption volume, and then the input light power at which it gets the saturation current is larger too, therefore its responsivity is slightly smaller than that of the vertical-illuminated uni-traveling carrier heterojunction phototransistor.