Nitride-based optoelectronic devices with nanoporous structures

• Main Authors: Bing-Cheng Hsieh, 謝秉承
• Other Authors: 林佳鋒
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/04344889895888554893

博士 === 國立中興大學 === 材料科學與工程學系所 === 103 === This thesis is divided into two parts about the InGaN-based optoelectronic devices with nanoporous structures. In the first part, the nanoporous (NP) structure is embedded into photon devices by using the electrochemical (EC) wet etching process. Then, the nanoporous GaN coverts into GaOx insulated layer through the photoelectrochemical (PEC) oxidation process as a current confinement structure. In the second part, a NP structure is introduced into the distributed Bragg reflectors (DBRs) using the EC wet etching process. The resonant cavity modes were observed in the light-emitting diodes (LED) with the NP-DBR structure. Part I illustrates a simple and robust process to convert embedded conductive GaN epilayers into insulating GaOx and demonstrate its efficacy in vertical current blocking and lateral current steering in a working LED device. The fabrication processes consist of laser scribing, EC wet etching, PEC oxidation, and thermal oxidization of a sacrificial n+-GaN:Si layer. The conversion of GaN is made possible by an intermediate stage of porosification where the standard n-type GaN epilayers can be laterally and selectively anodized into a NP texture while keeping the rest of the layers intact. The fibrous texture of NP GaN with an average wall thickness of less than 100 nm dramatically increases the surface-to-volume ratio and facilitates a rapid oxidation process of GaN into GaOx. The GaOx aperture was formed on the n-side of the LED between the active region and the n-type GaN layer. The observation of aperture-confined electroluminescence from an InGaN LED structure suggests that the NP GaN based oxidation will play an enabling role in the design and fabrication of III-nitride photonic devices. Part II demonstrates InGaN LEDs with embedded conductive nanoporous-GaN/undoped-GaN (NP-GaN/u-GaN) DBR. NP-DBR structures were fabricated by laser scribing and EC etching processes. Heavily Si-doped GaN layers (n+-GaN) in an eight-period n+-GaN/u-GaN stack structure were transformed into a low-refractive-index, conductive NP-GaN structure. The measured center wavelength, peak reflectivity, and bandwidth of the NP-GaN DBR structure were 417 nm, 96.7%, and 34nm, respectively. Resonance cavity modes of the photoluminescence spectra were observed in the LED with the NP-DBR structure.