Species from ambient atmosphere such as water and oxygen are known to affect electronic and optical properties of GaN, but the underlying mechanism is not clearly known. In this work, we show through careful measurement of electrical resistivity and photoluminescence intensity under various adsorbates that the presence of oxygen or water vapor alone is not sufficient to induce electron transfer to these species. Rather, the presence of both water and oxygen is necessary to induce electron transfer from GaN that leads to the formation of an electron depletion region on the surface. Exposure to acidic gases decreases n-type conductivity due to increased electron transfer from GaN, while basic gases increase n-type conductivity and PL intensity due to reduced charge transfer from GaN. These changes in the electrical and optical properties, as explained using a new electrochemical framework based on the phenomenon of surface transfer doping, suggest that gases interact with the semiconductor surface through electrochemical reactions occurring in an adsorbed water layer present on the surface.

中文翻译：

---

水和氧在GaN上的共吸附：电荷转移和电子耗尽层形成的影响

已知来自周围大气的物种（例如水和氧气）会影响GaN的电子和光学特性，但其潜在机理尚不清楚。在这项工作中，通过仔细测量各种吸附物下的电阻率和光致发光强度，我们发现仅氧气或水蒸气的存在不足以诱导电子转移到这些物质上。而是，水和氧气的存在对于从GaN引起电子转移是必需的，从而导致在表面上形成电子耗尽区。由于增加了从GaN的电子转移，暴露于酸性气体会降低n型电导率，而碱性气体由于减少的GaN电荷转移会增加n型电导率和PL强度。电气和光学特性的这些变化，