Influence Of Polarization Effects On AlGaN/GaN Heterojunction Pin Photodetectors

As a typical material of the third generation semiconductor, GaN-based material has advantages of wide band gap, high saturation velocity, high breakdown electric field and low dielectric constant, which has been widely applied in the fabrication of photo electric, high frequency and large power devices. Specially, the band gap of AlGaN alloy has a wide range from 3.4eV to 6.2eV for different Al fraction from 0 to 1, which covers all the solar-blind region. So, AlGaN-based material is a natural solar-blind material, which makes it has a wide application in the field of ultraviolet (UV) detecting. Recently, GaN-based UV detector has been researched widely and some research results have been obtained. Among them, GaN-based p-i-n structure UV detector is the key point gradually because of its advantage of high response speed, low noise and work well at bias voltage of zero.As well know, with the rapid development of microelectronic into the nanometer stage, the cost of the microelectronic devices fabrication and experiment is very expensive, the semiconductor process and physical mechanism of devices are becoming more and more complicated. TCAD(Technology Computer Aided Design) tools can be used to predict and optimize the semiconductor process and devices design by simulation and calculation, which is conducive to reducing the design cycle and cost. In this thesis, the influence of structure parameters, polarization effect and working temperature on the response of the AlGaN/GaN p-i-n structure UV detector is simulated and calculated by ISE-TCAD, and further discussion is presented taking the consideration of the band structure and electric field distribution. We obtain some results. First, with the increasing of i-GaN width from 50nm to 200nm, the response to the wavelength from 325 nm to 365nm is enhanced. However, the response to the wavelength of less than 325nm is reduced because of the reduction of noise. Secondly, for the same bias voltage, the introduction of polarization effect enhances the absorption for the wavelength of less than 325nm and decreases the absorption for the wavelength from 325nm to 365nm, which can be used to extend the active wavelength range. Thirdly, with increasing of temperature from 200K to 600K, the response of the detector almost does no change, which confirms the thermal stability of GaN-based material and GaN-based UV detector can be used in the harsh environment.