Open AccessImpact of Plasma Electron Flux on Plasma Damage‐Free Sputtering of Ultrathin Tin‐Doped Indium Oxide Contact Layer on p ‐GaN for InGaN/GaN Light‐Emitting Diodes
Author(s) -
Son Kwang Jeong,
Kim Tae Kyoung,
Cha YuJung,
Oh Seung Kyu,
You ShinJae,
Ryou JaeHyun,
Kwak Joon Seop
Publication year - 2018
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.201700637
Subject(s) - materials science , optoelectronics , indium tin oxide , light emitting diode , plasma , diode , doping , sputtering , indium , wide bandgap semiconductor , layer (electronics) , thin film , nanotechnology , physics , quantum mechanics
Abstract The origin of plasma‐induced damage on a p ‐type wide‐bandgap layer during the sputtering of tin‐doped indium oxide (ITO) contact layers by using radiofrequency‐superimposed direct current (DC) sputtering and its effects on the forward voltage and light output power (LOP) of light‐emitting diodes (LEDs) with sputtered ITO transparent conductive electrodes (TCE) is systematically studied. Changing the DC power voltage from negative to positive bias reduces the forward voltages and enhances the LOP of the LEDs. The positive DC power drastically decreases the electron flux in the plasma obtained by plasma diagnostics using a cutoff probe and a Langmuir probe, suggesting that the repulsion of plasma electrons from the p ‐GaN surface can reduce plasma‐induced damage to the p ‐GaN. Furthermore, electron‐beam irradiation on p ‐GaN prior to ITO deposition significantly increases the forward voltages, showing that the plasma electrons play an important role in plasma‐induced damage to the p ‐GaN. The plasma electrons can increase the effective barrier height at the ITO/deep‐level defect (DLD) band of p ‐GaN by compensating DLDs, resulting in the deterioration of the forward voltage and LOP. Finally, the plasma damage‐free sputtered‐ITO TCE enhances the LOP of the LEDs by 20% with a low forward voltage of 2.9 V at 20 mA compared to LEDs with conventional e‐beam‐evaporated ITO TCE.