High reliability GaAs metal-semiconductor - metal photodetectors with InGaP buffer and capping laye

Two metal-semiconductor-metal (MSM) structures designated as MSMl and MSM2 has been fabricated, and their performances have been compared. In MSM1, only an InGAP buffer layer and a GaAs absorption layer were grown on semi-insulating (100) GaAs substrate. While in MSMZ, another InGaP capping layer (500A) was grown on top of the GaAs absorption layer. All the epilayers were grown by low-pressure organometallic vapor phase epitaxy at 680°C, and the concentrations of the un-intentionally doped InGAP and GaAs layers. The variations of dark current with bias voltage of the two structures before and after thermal treatment are shown.