Growths and characterizations of GaN grown by two-heater MOCVD

• Main Authors: Cheng, Chun-Hung, 程峻宏
• Other Authors: Chen, Wei-Kuo
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/86454567625947700895

碩士 === 國立交通大學 === 電子物理系所 === 102 === We studied the fundamental issues which includes thermodynamic, hydrodynamic, and kinetic aspects of the growth process in MOCVD, both in the gas phase and on the surface. Two-heater MOCVD totally changed the gas phase phenomenon and the chemical reactions in the gas phase when compared with conventional MOCVD. By using gas phase thermal treatment with the ceiling temperature in two-heater MOCVD, the better optical quality with IYL/INBE reduced remarkably to 1/1000 and the crystalline quality with lower dislocation about 5x109 cm-2 of low temperature GaN films had been obtained. In order to find the reasons why two-heater MOCVD had the better low temperature GaN quality and higher growth efficiency, two series of sample had been used, substrate series and ceiling temperature series. From the analytical kinetic model for two-heater MOCVD and the experimental results of ceiling temperature series, we could found that both the enhancement of diffusivities and the thermophoretic force affected the mass transfer of the reactants in the reactor. As the result, the growth efficiencies would further increase when ceiling temperature were added. Base on the experiment results of the Arrhenius plot of growth efficiencies in conventional and two heater MOCVD. It seems that ceiling temperature supplied enough energy for the precursors in the gas phase made them to conquer the surface formation barriers, thus we could found that the growth efficiency reached the mass transport region when ceiling temperature had been used. When it comes to the development of long wavelength light emitting diodes (LEDs), such as green, amber and red LEDs, the growth temperature of GaN barrier should set below 900oC. In such low temperature the GaN films quality are worse. By using two heater MOCVD, high quality low temperature GaN films from 700℃ to 900℃ had been achieved, extending the growth window for the high quality GaN barrier of InGaN green LED and amber LED.