Optoelectronic properties of nonpolar a-plane GaN are superior along the [0002] azimuth direction compared to other azimuth directions. We have grown a-GaN on r-sapphire, and interdigitated electrode patterns of Au were fabricated to restrict the carrier transport only along [0002] azimuth. Surprisingly, the Schottky barriers of Au/GaN were found to be asymmetric in nature as the current on the positive side was different than negative for the same bias. Polarization on the boundaries of the basal plane defects has been already investigated for the possible reason of the Schottky barrier inhomogeneity. Thus, it can be expected that the overall effect of these polarization centers would change the Schottky barrier height of one of the electrodes. Electronic band-alignment based on asymmetrical contacts reveals that the difference in the Schottky barrier height would create a net electrical field toward the higher Schottky barrier, which is exploited here for self-powered photodetection and also enhanced photodetection at higher applied bias. The spectral response of all the devices was studied within 300–700 nm, and it was found that spectral response enhances with the applied voltage. The maximum responsivity and detectivity for a 364 nm light source observed at 5 V was around 400 A W^–1 and 6.6 × 10¹² jones, while at 0 V, it was 4.67 mA W^–1 and 3.0 × 10¹³ jones, respectively, which is the highest known responsivity for a-plane GaN to the best of our knowledge. The spectral response shows that the devices work for a very narrow band of radiation and hence can be used for selective UV-A photodetection. Overall, these results demonstrate much-improved UV photodetection properties compared to existing GaN-based photodetectors.

中文翻译：

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由非故意非对称电极驱动的高响应性，自供电的基于-GaN的UV-A光电探测器

与其他方位角方向相比，沿[0002]方位角方向的非极性a面GaN的光电性能优越。我们在r上生长了-GaN制作蓝宝石和相互交叉的Au电极图案以限制仅沿[0002]方位角的载流子传输。出乎意料的是，发现Au / GaN的肖特基势垒本质上是不对称的，因为对于相同的偏置，正极的电流不同于负极的电流。由于肖特基势垒不均匀的可能原因，已经研究了基面缺陷边界上的极化。因此，可以预料，这些极化中心的整体效果将改变其中一个电极的肖特基势垒高度。基于不对称接触的电子能带对准显示，肖特基势垒高度的差异会产生一个朝向较高肖特基势垒的净电场，在此将其用于自供电光电检测，并在更高的施加偏置下增强光电检测。在300-700 nm范围内研究了所有器件的光谱响应，发现光谱响应随施加的电压而增强。在5 V下观察到的364 nm光源的最大响应度和检测度约为400 AW^-1和6.6×10 ¹²琼斯，而在0V，这是4.67毫安W¯¯ ^-1和3.0×10 ¹³琼斯，分别，这是已知的最高响应一个面GaN的我们所知的。光谱响应表明，该设备适用于非常窄的辐射带，因此可用于选择性UV-A光检测。总体而言，与现有的基于GaN的光电检测器相比，这些结果证明了大大提高的UV光电检测性能。