The Growth and Fabrication of High Efficiency III-Nitride-Based Optoelectronic Device by Metal-organic Chemical Vapor Deposition

  • 游 俊達

學生論文: Doctoral Thesis

摘要

Growth and fabrication of high efficiency GaN-based optoelectronic devices were successfully demonstrated in this dissertation This dissertation proposed two directions to enhance the efficiency for fabrication of InGaN-based LEDs include the methods of Mg-doped AlGaN/InGaN superlattice electron blocking layer and digital InN/GaN growth in InGaN well We also proposed two methods to improve the efficiency of InGaN-based solar cells by introducing ex-situ AlN nucleation layer and Si-doped AlGaN barriers Firstly the operating voltage light output power and efficiency droops of GaN-based light emitting diodes (LEDs) were improved by introducing Mg-doped AlGaN/InGaN superlattice (SL) electron blocking layer (EBL) The thicker InGaN layers of AlGaN/InGaN SL EBL could have a larger effective electron potential height and lower effective hole potential height than that of AlGaN EBL This thicker InGaN layer could prevent electron leakage into the p-region of LEDs and improve hole injection efficiency to achieve a higher light output power and less efficiency droops with the injection current The low lateral resistivity of Mg-doped AlGaN/InGaN SL would have superior current spreading at high current injection Secondly thick InGaN wells of LEDs with high crystal quality can be prepared by using digital InN/GaN growth for the InGaN wells The thickness of high crystal quality InGaN wells can be sustained with In% of 17 6% more than 7 nm The 60 mA output power of LEDs with thick InN/GaN alternative growth InGaN wells indicate an enhancement of at least 28 9% compared with that of LEDs with conventional InGaN wells However LEDs with thick InN/GaN alternative growth InGaN wells have larger efficiency droops than LEDs with conventional InGaN wells Compared with conventionally grown thin InGaN wells thick InGaN wells with digitally grown InN/GaN exhibit superior optical properties The activation energy (48 meV) of thick InGaN wells (generated by digital InN/GaN growth from temperature-dependent integrated photoluminescence intensity) is larger than the activation energy (25 meV) of conventionally grown thin InGaN wells Moreover thick InGaN wells with digitally grown InN/GaN exhibit a smaller ? value (the degree of localization effects) of 19 meV than that of conventionally grown thin InGaN wells (23 meV) Thirdly GaN solar cells (SCs) with ex-situ AlN nucleation layer are examined in this study GaN with sputtered ex-situ AlN nucleation layer has mixed-type dislocation density at approximately one order less than that of GaN with in-situ GaN nucleation layer The reduction of dislocation density by the sputtered AlN nucleation layer could suppress the reverse leakage current and the recombination forward current in low forward voltage range of SCs and then can increase Jsc and Voc of the SCs 1-sun η% of SCs with ex-situ AlN nucleation (1 92%) showed an enhancement of 27 2% compared with that of conventional SC at 1 51% Furthermore the 100-sun η% of SCs with ex-situ AlN nucleation (1 99%) showed 18 5% improvement compared with that of conventional SC (1 68%) Finnaly the Voc FF% and η% of GaN-based SCs can be improved by replacing an initial 2-pair GaN/InGaN with 2-pair AlGaN/InGaN multilayer The IPCE of SCs with 2-pair AlGaN/InGaN multilayer is higher than that with GaN/InGaN at 2 V for wavelengths in range of 365 nm to 420 nm From the results of the numerical simulation we found that the FF% improvement of the SCs with the 2-pair AlGaN/InGaN multilayer should be attributed to the photo-generated carrier recombination rate suppression near the bias of the Voc The 1-sun η of SCs with Si-doped Al0 10GaN barriers (1 86%) showed 27 4% enhancement compared with that with Si-doped GaN barriers (1 46%)
獎項日期2015 二月 13
原文English
監督員Wei-Chi Lai (Supervisor)

引用此文

The Growth and Fabrication of High Efficiency III-Nitride-Based Optoelectronic Device by Metal-organic Chemical Vapor Deposition
俊達, 游. (Author). 2015 二月 13

學生論文: Doctoral Thesis