High-speed InP-based In/sub x/Ga/sub 1-//sub x/As Schottky barrier infrared photodiode for fiber-optic communications

We report on a new high-speed InP-based In/sub x/Ga/sub 1-//sub x/As Schottky barrier photodiode for infrared detection. The photodiodes were fabricated on both p- and n-InGaAs epilayers. For this application, Schottky barrier height enhancement on InGaAs has been demonstrated. The photodiodes had responsivities as high as 0.55 A/W and quantum efficiencies of up to 45% in the range of 1.3--1.6 ..mu..m without antireflection coating. The response speed of photodiodes was measured by the impulse response and autocorrelation methods; rise times of 85 ps for p-InGaAs and 180 ps for n-InGaAs photodiodes were obtained. Recently, a barrier height enhancement of 0.35 eV was obtained in n-InGaAs photodiodes, resulting in a great reduction of leakage currents. This would lead to further improvement in the device performance of the photodiodes. Based on measured RC time constants, we estimate the intrinsic response speed to be 12 GHz for n-InGaAs and 18 GHz for p-InGaAs photodiodes. These results show that InP-based In/sub x/Ga/sub 1-//sub x/As Schottky barrier photodiodes can be very useful for high-speed infrared receivers in fiber-optic communications.