Investigation and fabrication of GaN-and AlGaInP-Based light-emitting diodes by nanostructures

Abstract

The main purpose of this dissertation is to develop high efficiencies of GaN- and AlGaInP-based light-emitting diodes (LEDs) by applying nanostructures Research to improve the GaN light-emitting diodes in the application of nanostructures improve the light output power of the GaN-based light emitting diodes (LED) In this paper we used several kinds of plasma on p-GaN We expect to let the bottom of the p-pad region nearly insulated by using the optimal plasma treatment condition Because the light below the p-pad will be eclipsed or reflected by the thick p-pad this result will reduce the efficiency of output power Therefore we could get the higher output power by reducing the current below the p-pad region We can get 13% enhancement in light output power at 20 mA The second part the effect of the etching pattern and etching depended on the aspect ratio on the characteristics of the GaN-based LEDs would be discussed We successfully demonstrated that the GaN-based LEDs with nano-patterns by contact-transferred and mask-embedded lithography (CMEL) and use inductively coupled plasma (ICP) dealing with p-type GaN film surface and applying to the GaN light emitting diodes (LEDs) to discuss how ICP power time treatment and the changing in Cl2/N2 gas rates influence plasma etching with in-situ N2 treatment on electric characteristics and light output efficiency we investigate the use of patterned structures in the light-emitting diodes and improve the light extraction efficiency Applied simple low-cost CMEL to texture p-GaN for the fabrication of GaN light-emitting diodes (LEDs) for the LEDs without CMEL with CMEL-3 μm and with CMEL-400 nm We were also found that the 20 mA light output power were 4 28 mW 4 59 mW and 5 16 mW respectively Al-doped ZnO (AZO) thin film contact to AlGaInP-based light emitting diode(LED) was investigated and compared with ITO thin film We demonstrated a series of properties of different transparent contact layers(TCL) onto p-GaP and applied the optimization to the chip process of LEDs In order to improve the electrical properties of AZO contact layer to p-GaP the direct ohmic contact structure is performed by the deposition of an AuBe diffused thin layer on the surface of GaP window layer After a best annealing treatment process which can effectively improve the contact characteristics The specific contact resistances could be further reduced from could be further reduced from 2 68 × 10?4 to 1 52 × 10?4Ω-cm2 Based on the above TCL conditions AlGaInP LEDs featured with AZO and ITO film as current spreading layer (CSL) application AlGaInP LED used in surface roughening after With an injection current of 20 mA these LEDs light output powers of 7 01mW and 6 6mW the maximum output power could be enhanced 49 6% The material of AZO shows the superior electrical properties and reliability the AZO thin film deposited by electron-beam evaporator could be a transparent electrode application on AlGaInP-based light emitting diode Nanorods ZnO layers were fabricated on the top of the p-GaP window layers of AlGaInP-based LEDs by using Successive Ionic Layer Adsorption and Reaction (SILAR) method However GaP window layer with ZnO nanorods mask were etching by ICP process the maximum output power could be enhanced 78 34% under 20mA current injection as compared with the standard surface LEDs The use nanostructures in order to increase the improvement of GaN-based LEDs and the AlGaInP-LEDs light output efficiency The First part the use ZnO nanorods were grown by Successive Ionic Layer Adsorption and Reaction (SILAR) method This experiments were carried out at low temperature 95°C and at normal pressure conditions ZnO nanorods with different diameters and densities were grown on SiO2 thin films on surface or GaN-based LEDs by controlling DI water and ethylene glycol rinsing procedures with different solvent volume ratios (water/ethylene glycol) After the SiO2 thin films on GaN-based LEDs was etching by ICP the output power variation voltage variation and wavelength spectrums of GaN-based LEDs were investigated The output power could be enhanced 42 7%–49 1% under 20-mA The second part the use ratio of DI water and ethylene glycol by Successive Ionic Layer Adsorption and Reaction (SILAR) method The sizes and the distribution of SiNx nanopillars on AlGaInP-based LEDs are observed by Scanning Electron Microscopy (SEM) and Particle Analyzer we apply SiNx nanopillars as a hard mask to obtain patterned and roughing wafer surface by which the light extraction the light-output power was significantly increased by a factor of 33 7% than conventional structure under 20-mA operation

Date of Award	2014 Aug 2
Original language	English
Supervisor	Shoou-Jinn Chang (Supervisor)