Novel Ohmic Contact Technology to P-type and N-type GaN

欧姆接触对n型和p型GaN、AlGaN和GaInN的比电阻对器件的许多性能非常重要，如功率效率、放大、噪声、器件发热和可靠性。在这项工作中，将开发和研究一种全新的方法来实现AlGaN、GaInN和GaN的低阻欧姆接触。这种接触是基于GaN及其相关化合物中存在的强自发极化场和压电极化场。金属-半导体接触近表面层中的极化场将增加载流子的隧穿几率，从而降低欧姆接触比电阻。将发展有关隧穿概率、接触形成和比接触电阻的理论和模型。将演示极化增强型接触，并验证降低的接触电阻。此外，还将研究极化场在AlGaN-GaN超晶格中的作用，并对超晶格进行欧姆接触应用的优化。这项工作的一个组成部分将是将极化增强型欧姆接触纳入光电子和电子器件。发光二极管(LED)，特别是用于大功率照明应用的LED，需要低电阻欧姆接触，以减少器件发热，提高器件效率和可靠性。将演示具有极化增强型欧姆接触的GaN/GaInN LED。偏振增强型欧姆接触也将在激光器和晶体管中实现，这些器件性能的改善将是demonstrated.******************************************************************

The specific resistance of ohmic contacts to n- and p-type GaN, AlGaN, and GaInN are very important for many device properties such as power efficiency, amplification, noise, device heating, and reliability. In this work, a fundamentally novel approach to low-resistance ohmic contacts to AlGaN, GaInN, and GaN will be developed and investigated. The contacts are based on the employment of the strong spontaneous and piezoelectric polarization fields occurring in GaN and related compounds. The polarization fields in the near-surface layers of metal-semiconductor contacts will enhance the tunneling probability of carriers thereby reducing the ohmic contact specific resistance. The theory and modeling pertaining to tunneling probability, contact formation, and specific contact resistance will be developed. Polarization-enhanced contacts will be demonstrated and reduced contact resistances will be verified. In addition, the role of polarization fields in AlGaN-GaN superlattices will be investigated and the superlattices will be optimized for ohmic contact applications. An integral part of the work will be the incorporation of the polarization-enhanced ohmic contacts in optoelectronic and electronic devices. Light-emitting diodes (LEDs), in particular LEDs used for high-power illumination applications, are in need of low resistance ohmic contacts in order to reduce device heating and improve device efficiency and reliability. GaN/GaInN LEDs with polarization-enhanced ohmic contacts will be demonstrated. Polarization-enhanced ohmic contacts will also be realized in lasers and transistors and improved properties of these devices will be demonstrated.******************************************************************