Ohmic contact mechanism for RF superimposed DC sputtered-ITO transparent p-electrodes with a variety of Sn2O3 content for GaN-based light-emitting diodes

Abstract The dependence of the electrical and optical properties of radio frequency (RF) superimposed direct current (DC) sputtered–indium tin oxide (ITO) on the tin oxide (Sn 2 O 3 ) content of the ITO is investigated, in order to elucidate an ohmic contact mechanism for the sputtered-ITO transparent electrodes on p-type gallium nitride (p-GaN). Contact resistivity of the RF superimposed DC sputtered-ITO on p-GaN in LEDs decreased when Sn 2 O 3 content was increased from 3 wt% to 7 wt% because of the reduced sheet resistance of the sputtered-ITO with the increasing Sn 2 O 3 content. Further increases in Sn 2 O 3 content from 7 wt% to 15 wt% resulted in deterioration of the contact resistivity, which can be attributed to reduction of the work function of the ITO with increasing Sn 2 O 3 content, followed by increasing Schottky barrier height at the sputtered ITO/p-GaN interface. Temperature-dependent contact resistivity of the sputtered-ITO on p-GaN also revealed that the ITO contacts with 7 wt% Sn 2 O 3 yielded the lowest effective barrier height of 0.039 eV. Based on these results, we devised sputtered-ITO transparent p-electrodes having dual compositions of Sn 2 O 3 content (7/10 wt%). The radiant intensity of LEDs having sputtered-ITO transparent p-electrodes with the dual compositions (7/10 wt%) was enhanced by 13% compared to LEDs having ITO with Sn 2 O 3 content of 7 wt% only.