Employment of III-nitride/silicon heterostructures for dual-band UV/IR photodiodes

Abstract

Employment of layered structures made of semiconductor materials with different optical absorption bands is a new way of realizing either broad band spectrum or selective multiple band photodetectors. A new concept of structures fabricated using stacked semiconducting layers to obtain a multi band spectral response is reported. Based on this approach, fabrication of a Solar-blind dual-band UV/IR photodetectors is demonstrated. Optimization of the device was carried out by modeling of the electric field distribution and developing tunneling barriers. The optimized Solarblind UV/IR photodiode UV spectral response turns-on approximately around 265 nm (solar-blind) and peaks at 230 nm with a responsivity of approximately 0.0018 A/W. The IR diode response peaks at 1000nm with a responsivity of approximately 0.01 A/W. I.IntroductionBinary and Ternary III-Nitride materials are gaining more interest in the field of imaging given their tunable direct band gap properties ranging from 6.2eV [1, 2] to 0.7eV [3]. They are superior to other materials due to their high thermal, chemical, mechanical, and radiation tolerance. Several groups have dedicated a large amount of research to the development of UV detectors based on GaN [4-10], GaN/AlGaN [11][12][13], and AlGaN [14]. Currently, attracting the most interest are AlGaN-based structures since they allow detection in the very important UV range of 240-280 nm, which corresponds to the absorption of solar radiation by the ozone layer [15] and InGaN-based structures absorbing in the 1.75-2.5eV range important for advanced solar cell development.The importance of infrared detection, which was initially motivated by night vision and thermal sensing, took a big leap with the boom of the telecommunication optical fiber industry. Recently, Ge y Sn 1-y [16] alloys were used as photoconductors for detection of wavelengths at 1.55μm. Conventional HgCdTe-[17] and InSb-based IR detectors display high quantum efficiencies, but are difficult to integrate into large arrays. Detectors based on heterointernal photoemission (HIP) in Ge x Si 1-x /Si heterojunctions have demonstrated excellent opportunities for integration on Si wafers at sufficient sensitivities in the infrared range of 1-12 μm [18][19][20][21]. Large area SiGe-based HIP photodetector arrays of 400x400 pixels have been available for close to ten years [22]. Metal silicide [23,25] based photodetectors have shown the extension of IR detection based on silicon. However, such devices are limited to operations under cooled conditions, such as cryogenic temperatures or even lower. The opportunity to grow IIINitrides on Si wafers is considered as one of the main approaches in the development of multi-color detectors for wavelengths ranging from the UV to IR.The major advantages of multi-band solid state photodetector structures is their potential integration into multi-pixel focal plane arrays (FPA) for imaging applications critical in recognition of various events that result in optical emission. This feature allows for added accuracy...