Low resistance ohmic contacts to p-InP of mesa-isolated InP/InGaAs PIN photovoltaic detectors

The electrical and metallurgical behavior of Ti/Pt/Au contacts on p-InP was investigated. The contacts were transformed to an ohmic contacts at the temperature about 450 ℃. Low resistance ohmic contacts (c=7.310-5cm2) were achieved after annealing at 450 ℃ for 4 minutes. To approach device process, Cr/Au (20 nm/400 nm) was deposited on the contact pads after the annealing process. The result indicates that the contacts of low resistance, smooth surface and high reliability are fabricated in a moderate condition. The auger electron spectroscopy(AES) depthcomposition profiles indicates that the Pt layer can relatively prevent Au from penetrating into the InP and only a small quantity of Au punched through the Pt layer and penetrated into the InP. The findings of the present study suggests that the formation of ohmic contacts on InP is controlled by chemical and metallurgical reaction between the contact metal and the InP layer, and a few InAux formations are beneficial to contact properties.