Photoconductivity Of Gan-based Light Guide Device And Uv Film Material Uniformity Testing System

As a kind of broad direct-gap semiconductor material, GaN-based materials attract much attention in making high temperature, high power and high frequency electronic devices as well as light emitting diodes, laser diodes and photo-detectors due to their excellent physical and chemical performances.In this paper, our works focus on the characteristics of the GaN-based materials, manufacture and test of the photoconduction detector with unintentional doped n-GaN. In the experiment, we have found that the change of the incident intensity obviously influences the photo-conductivity curve, and the photo-current increases with the augment of the incident intensity. When the wavelength of the incident light is larger than the intrinsic-absorption wavelength of GaN, the photoconduction devices will change from Photocurrent (PC) and Persistent Photocurrent (PPC) to Negative Photocurrent (NPC) and Negative Persistent Photocurrent (NPPC) along with the increase of the incident intensity. It's believed that the photocurrent is ruled by competition between capture of conduction band electrons by deep electron traps and recombination with trapped -holes.The uniformity of the materials can be estimated by analyzing the transmittance of materials. Using this method, we have developed a set of system to measure the uniformity of UV-film materials, which consists of Xenon-lamp, monochromator, optical setup, 2D stepping motor, photoelectric detector, and data record instrument, etc.. Using the Lab VIEW software, the non-uniformity of the materials can be tested and estimated quantitatively without scathing the materials. In addition, we have also used this system to test the GaN-based epitaxial wafer grown with different structure parameters and growth conditions. The experimental results show that the uniformity of Al_0.65Ga_0.35N single-wafer material is better than that of the Alo.45Gao.55N and Al_0.3Ga_0.7N ones; the uniformity of materials with buffer-wafer annealed in 1000s or in high and low temperature is better than those with buffer-wafer annealed in 300s or in low temperature only, respectively; the uniformity of materials which are boat rotated in the grown time is better than those not-rotated. In conclusion, this system can test and filter the wafer before the chip fabrication, reducing the influence of the unqualified wafer on the device's uniformity, which greatly saves much energy and money.