The Design And Fabrication Of High Voltage GaN LED

Light emitting diode (LED) is widely adapted for its t high luminous efficiency,environmental protection and long life-span characteristics. With the incandescentlamp exiting lighting market, LED has got vaster development space. However，thehigh-voltage LED (HV LED) substitutes the role of incandescent lamp because of thecharacteristic of high-voltage and small current driven.Since the time of studying HVLED is not sufficient, there are many problems in designing and fabricating HV LED.So it is valuble to study HV LED.This paper is supported by the National Key Technologies R&D Program (No.2011BAE01B14). the layout of50V High-voltage LED was designed,At the sametime，the layout of100V HV LED,200V HV LED were designed first time by themethod of interconnection process. The structures and the methods to improve thelight extraction efficiency were studied. The key fabrication process of HV LED wasoptimized. The micorodisplay was designed and fabricated the first time, which isadvance in China and last designed the driver circuit to drive the microdisplay.Thedetail contents of the study are as follow:(1) Designed the layout of50V High-voltage LED; the parameters of GaN waferwere measured according to Transmission Line Model and the sheet resistance ofP-GaN, N-GaN and ITO and the specific contact resistance of ITO and P-GaN werecalculated. Power and small power LEDs were fabricated at the same condition.Thecurrent distribution and the voltage were compared.According to the result，the layoutof HV LED was designed.At the same time，the layout of100V HV LED,200V HVLED were designed first time.(2) Studied the structures and the methods to improve the light extractionefficiency. The LEDs with SiO2layer textured， ITO layer textured and mesatexturedwere fabricated. The light characteristics were measured and compared withthe LED with original structure. At the same time, the LED with the current blocklayer(CBL)，DBR backside reflector and the LED fabricated with the pattenedsubstrate GaN wafer were fabricated in the experiment. The light characteristics werealso measured and compared with the LED with original structure.(3)Optimized the key fabrication process of HV LED.Firstly, The material oflithography mask in ICP etch and the relationship of ICP etch and the ITO etch were studied, and the condition of ITO etch was obtained in the experiment. Secondly，designed different conditions of ITO annealing in the experiment to optimize theelectrical and optical characteristic of LED.Last，According to experimental analysisand theoretical model for the affect of the series resistance in GaN on light efficiency，the material of electrode was optimized.50V HV LED was fabricated in theoptimized process.The voltage is48V and the radical flux is314mw(4)Designed and fabricated the LED microdisplay chip. Firstly, the layout of LEDmicrodisplays with different pixel sizes were designed, which is in the domesticleading position in china.Secondly, the key fabrication process were optimized. Twosetps etch and ‘two times deposition’ methods were used in the ICP tech process andfilm deposition process respectly.Finally, the electrical and optical characteristicswere measured and compared. The thermal characteristic was studied.(5)Designed the drive circuit to drive the microdisplay.In the circuit the16-bitMCU SPCE06A made in Lingyang Company was used to light the microdisplay bythe method of dynamic scanning and a simple character was displayed successfully.