Structural design of dual carrier multiplication avalanche photodiodes on InP substrate

Avalanche photodiodes are widely used in various fields, such as optical communication and laser radar, because of their high multiplication. In order to adapt to very weak signal detection applications, devices are required to have higher gain values. The existing avalanche photodiodes generally use single carrier multiplication mode of operation, its multiplication effect is limited. In this paper is designed an InP/In_0.53Ga_0.47As/In_0.52Al_0.48As avalanche photodiode structure with electrons and holes jointly involved in multiplication. In this structure, In_0.53Ga_0.47As material is used for the absorption layer, InP material is used for the hole multiplication layer, In_0.52Al_0.48As is used for the electron multiplication layer, and the two multiplication layers are distributed on the upper side and lower side of the absorber layer. Under the reverse bias, the photogenerated electrons and the absorber-layer generated holes can enter into the respective multiplier layers in different directions and create the avalanche multiplication effect, so that the carriers are fully utilized. This structure and the conventional single multiplication layer structure are simulated by Silvaco TCAD software. Comparing the single InP multiplication layer structure with the single In_0.52Al_0.48As multiplication layer structure, the gain value of the double multiplication layer structure at 95% breakdown voltage is about 2.3 times and about 2 times of the former two, respectively, and the device has a larger gain value because both carriers are involved in multiplication in both multiplication layers at the same time. The structure has a dark current of 1.5 nA at 95% breakdown voltage, which does not increase in comparison with the single multiplication layer structure, owing to the effective control of the electric field inside the structure by multiple charge layers. Therefore, this structure is expected to improve the detection sensitivity of the system.