Study On InP-based Near-infrared Photodetector

In this work,the indium-phosphide(InP)based near-infrared photodetectors have been studied.We designed,manufactured and tested the devices.The graphene/indium phosphide(Gr/InP)Schottky contact characteristics,the electrical properties of PIN and PNP structure of InP/InGaAs and InAlAs/InGaAs photodetectors have been deeply analyzed.Firstly,we studied the Schottky contact characteristics between Gr and InP of n-type and p-type.Using the model of Thermionic Emission(TE)to extract the barrier height and ideal factor of the device from the current-voltage(?-?)curve,we found the Gr/p-InP Schottky barrier height is higher(0.88 eV)and the ideal factor(3.06)is smaller than Gr/n-InP.In order to further understand the contact characteristics,capacitance-voltage(C-V)characteristics was tested and we found that the C-V characteristics of the two contacts were different.The capacitance of Gr/p-InP contact increases with the increase of reverse bias voltage,and the C-V curve of Gr/n-InP contact has a peak,which mainly results from the trap level of the contact interface.Then,by optimizing the structure and parameters of devices,we obtained a InGaAs/InAlAs infrared photodetector of PIN structure with high responsivity(0.9 A/W)and low dark current(4.04×10-6 A/cm2).The C-V characteristics of the structure were also studied.It was found that the capacitance increases first and then decreases with the increase of voltage.There is a capacitance peak appearing,and the peak value decreases with the increase of the frequency.Finally,according to the function of current amplification of heterojunction phototransistors,we prepared and analyzed a InGaAs/InP infrared photodetector of PNP structure with two-terminal.The device has a large current response(694 A/W)at lower operating voltages,realized the photocurrent amplification,and the responsivity increases with the applied voltage increasing.