Simulation Of The Dark Current Characteristics Of The Vertical PIN Type Ge/Si Quantum Dot Infrared Photodetectors

The quantum dot infrared photodetectors (QDIPs) have promising application prospects in the field of infrared detection. The excellent characteristics of the QDIPs over the quantum well infrared photodetectors (QWIPs) are lower dark current, high photoconductive gain, long lifetime of photoproduction carrier, increased operating temperatures, high quantum efficiency, and sensitivity to normally incident infrared radiation. In recent years the QDIPs have already become the research hotspots. Especially the main advantages of vertical PIN type Ge/Si QDIPs are that preparation process is compatible with mature large-scale integrated circuit technology,that vertical structure can easily be made infrared focal plane array (FPA), that the merit of PN junction is lower dark current to improve the detection rate, and that by appropriately controlling the growth parameters to adjust the energy band structure,device can achieve rapid response of these significant optical fiber communication wavelengths(1.31and1.55μm).So in recent years they have attracted more attention from the researchers around the world.However, the dark current and its corresponding noise of the device are generally higher than that of the QWIPs, which restricts the further application of Ge/Si QDIPs. If the dark current is too large, it will directly affect the Signal to Noise Ratio (SNR), responsivity, and detectivity. So the numerical simulation analyses of the dark current characteristics of vertical PIN type Ge/Si QDIPs need to be investigated in detail, which can provide some theoretical guidances for the experiments and also play significant roles in improving the performance of the device.Unlike multi-layer film structure and QWIPs, the main components of the dark current in QDIPs are the thermionic emission and field-assisted tunneling.Therefore, in this thesis the physical models of the thermionic emission and field-assisted tunneling mechanisms are established to analyse the main sources of dark current. On the basis of this, the physical model the dark current characteristics of the vertical PIN type Ge/Si QDIPs is gained.The specific calculation results are as follows:1. The bias voltage and temperature characteristics of the dark current of the monolayer QDIPs are calculated. They are compared with the experimental value of same device structure.The dark current is qualitatively analyzed at different quantum dot(QD) density∑QD、temperature T, and bias voltage V.2. The effects of parameter changes,such as temperature T, bias voltage V, the thickness of blocking layer L, QD density∑QD, the lateral characteristic size of QDs αQD, and total number of the QD layers M, on the dark current of the device are investigated in detail. The effects of the thermionic emission and field-assisted tunneling mechanisms on the dark current at different temperatures and bias voltages also are studied. Comparing the simulation data with the experimental data, we verify the accuracy of the physical model and algorithm.