A Study Of Performance Of GaN-Based P-i-n-type UV Detector

With the development of science and technology, detection technology advances increasingly. The technologies of infrared detection and laser detection which appeared in the early time, have been unable to meet people’s needs. The emerging UV detection technology catches more and more attention, and it occupy an important seat in both military and civilian. Ga N-based p-i-n-type UV detector has several advantages, such as low operating voltage, high input impedance, low dark current, becoming a major direction of development of UV detectors. This thesis is focused on optimization of the Ga N-based p-i-n UV detectors and analyze their performance. According to the working principle of p-i-n UV detectors, we analysis the effect of the performance of the detectors by different intrinsic i-layer thickness and different sizes. We analyzed the performance of the detector in detail by characterizing its crystalline quality, I-V characteristics, C-V characteristics and spectral response characteristics. Then the detector is processed into different sizes to comparative analysis their light and dark current ratio.We find that if we optimize the thickness of i-Ga N layer, the crystalline quality can be improved. In this paper, the thickness of i layer of the best wafer is 990 nm. According to the formula, the densities of screw and edge dislocations are 3.6 1011 cm-2 and 8.8 1011 cm-2. With the increase of thickness, the dislocation density can be reduce and the crystal quality can be improved. We analysis the I-V curves, C-V curves and spectral response of the wafer. The I-V curves show that leakage current is only 0.19 p A, and photocurrent is 66 n A under 1V reverse bias, differing by 5 orders of magnitude. It indicates that i layer has strong ability of effective absorption, and high generation rate of photo carrier. The doping concentration of i layer can be obtained by the C-V curves. Obtained by the spectral response curves, the photocurrent reaches 4.56 10-8 A, spectral responsivity is 0.18 A/W under the UV of 355 nm. The results describe that the device has good performance and is worthy of continued study.We compare and analysis the I-V curves of the photocurrent and dark current in different sizes of the detectors. Experimental results indicate that with the increase of the size of the chip, dark current and photocurrent are both increased under the same bias. The results of this experimental is that the best device has a ratio of light and dark current of 6.1 105 under 5V reverse bias, and its size centered in all samples. It shows that it is very necessary to choose the right size.