New wide-gap semiconductor materials for opto-electronics and for fundamental research

2014年诺贝尔物理学奖“因为发明了高效的蓝色发光二极管(LED)，使之成为明亮节能的白色光源”，不仅在学术界，而且在商业层面上，重新唤起了人们对宽带隙材料的兴趣。随着生长技术和第一批LED由雅克·艾萨克·潘科夫在20世纪70年代开发出来，不幸的是，基于氮化镓(GaN)的化合物半导体器件往往生活在基于砷化镓(GaN)的同类器件的阴影下。GaN作为具有大禁带隙半导体的唯一代表，为进入一类新兴的具有小发射波长和高突破电压的商业器件提供了可能性，但也允许探索一种以前未被探索的介观物理领域，因为与传统的GaAs或Si(Si)系统不同的本征材料性质。由于宽禁带系统中电子-电子相互作用的增强，预计会偏离单电子图像而形成准粒子。遗憾的是，宽带隙材料的生长还没有达到像GaAs或Si那样的成熟度。虽然GaN薄膜的制备技术与GaN几乎相同，但高迁移率的二维电子气(2DEGs)的制备受到衬底质量和可用性的阻碍。我们致力于在可获得的最高质量衬底上生长超纯GaN/AlGaN异质结，其目标是展示超出报告的电子迁移率、新颖的电子和光电子器件概念以及探索以前无法进入的介观地形。我们的想法是指在相同的实验条件下，对参数相近的GaN/AlGaN、ZnO/MgZnO和GaAs/AlGaAs异质结进行比较研究。例如，我们计划研究宽带隙系统中的电子等离子体特性，并开发用于微波辐射的快速探测器和调制器。工作在100-200 GHz载频的高速无线通信设备的原型确保信息速率高达50Gbit/S将是一个实际的结果。此外，对这些具有强相互作用和大质量的新型2D电子系统的关联效应和费米液体效应的研究也为多粒子物理提供了一个新的视角，即分数量子霍尔效应。在项目过程中获得的知识可以成为开发用于经典和量子电子学的新型微型半导体元件的基础。

The 2014 Physics Nobel prize “for the invention of efficient blue light-emitting diodes (LED) which has enabled bright and energy-saving white light sources” refreshed the interest in wide band-gap materials not only on an academic, but also on a commercial level. With growth techniques and first LEDs developed in the 1970s by Jacques Isaac Pankove, unfortunately compound semiconductor devices based on Galliumnitride (GaN) tended to live in the shadows of their Galliumarsenide-based (GaAs) counterparts. GaN as only one representative of semiconductors with a large band-gap offers the possibility to step into an emerging class of commercial devices exhibiting small emission wavelength and high-breakthrough voltage, but also allows to probe an previously unexplored regime of mesoscopic physics due to different intrinsic material properties compared to the traditional systems GaAs or Silicon (Si). As a consequence of enhanced electron-electron interactions in wide band-gap systems, deviation from the single electron picture towards the formation of quasi-particles is expected. Unfortunately the growth of wide band-gap material has not reached the maturity as GaAs or Si. While GaN thin films are synthesized with almost identical growth techniques like GaAs, the fabrication of e.g. high-mobility 2-dimensional electron gases (2DEGs) is impeded by substrate quality and availibilty. Our effort on launching a cost- and labor-intense campaign to growth ultra-pure GaN/AlGaN heterostructures on the highest-quality substrates accessible aims at the ultimate goal to demonstrate electron mobilities exceeding reported values, novel electronic and optoelectronic device concepts as well as the exploration of previously inaccessible terrains in mesoscopia. Our ideas imply comparative studies of GaN/AlGaN, ZnO/MgZnO and GaAs/AlGaAs heterostructures with similar parameters under identical experimental conditions. For example, we plan to investigate electron plasma properties in wide band-gap systems and to develop fast detectors and modulators for microwave radiation. Prototypes of high-speed wireless communication devices operating at 100-200 GHz carrier frequency ensuring information rates up to 50 Gbit/s will be a practical consequence. In addition the investigation of correlation and fermi-liquid effects in these novel 2D electron systems with strong interaction and heavy mass enables a new view on many-particle physics, namely the fractional quantum Hall effect. The knowledge gained in the course of the project could become a basis for the development of a new class of miniature semiconductor elements for classical and quantum electronics.