High-efficiency unitraveling-carrier photodiode with an integrated total-reflection mirror

A novel photodiode (PD) structure with an integrated total-reflection mirror which can enhance the quantum efficiency in back-illuminated geometry is proposed. Due to the diagonal propagation of the reflected light at the total-reflection mirror through the absorption layer, the efficiency is improved by about 50% from that of the normally irradiated case. By employing a unitraveling-carrier structure together with a thick absorption layer of 4700 A, the fabricated PD exhibits a high responsivity of 0.65 A/W, a high 3-dB bandwidth of 50 GHz, and a high-output voltage of 5 V, simultaneously.