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

2014年物理学诺贝尔奖“因发明高效蓝色发光二极管（LED）而获得，该二极管实现了明亮且节能的白色光源”，不仅在学术上，而且在商业层面上重新激发了人们对宽带隙材料的兴趣。随着Jacques Isaac Pankove在20世纪70年代开发的生长技术和第一个LED，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（GaAs）的对应物的阴影中。GaN作为具有大带隙的半导体的唯一代表，提供了进入新兴类别的商业器件的可能性，这些器件表现出小的发射波长和高的突破电压，但由于与传统系统GaAs或硅（Si）相比不同的固有材料特性，也允许探测先前未探索的介观物理机制。作为增强的宽带隙系统中的电子-电子相互作用的结果，预期从单电子图像朝向准粒子的形成的偏差。遗憾的是，宽带隙材料的生长还没有达到GaAs或Si那样的成熟。虽然GaN薄膜是用与GaAs几乎相同的生长技术合成的，但例如高迁移率二维电子气（2DEG）的制造受到衬底质量和可用性的阻碍。我们致力于发起一项成本和劳动密集型的运动，在最高质量的衬底上生长超纯GaN/AlGaN异质结构，其最终目标是展示电子迁移率超过报告值，新颖的电子和光电器件概念以及在介观中探索以前无法到达的地形。我们的想法意味着GaN/AlGaN，ZnO/MgZnO和GaAs/AlGaAs异质结在相同的实验条件下具有相似的参数进行比较研究。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。在100-200 GHz载波频率下运行的高速无线通信设备的原型将确保高达50 Gbit/s的信息速率，这将是一个实际的结果。此外，在这些新的强相互作用和重质量的二维电子系统中的关联和费米液体效应的研究，使一个新的观点，多粒子物理，即分数量子霍尔效应。在项目过程中获得的知识可能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.