Room-temperature Ohmic contact on n-type GaN with surface treatment using Cl2 inductively coupled plasma

Abstract

A room-temperature Ti/Al Ohmic contact on n-type GaN was obtained by surface treatment using Cl2 inductively coupled plasma treatment. The specific contact resistivity was dramatically decreased from the Schottky behavior to 9.4×10−6 Ω cm2 by the treatment. The binding energy of the Ga–N bond and the atomic ratio of Ga/N were simultaneously increased after the plasma treatment. This provides evidence that N vacancies, acting as donors for electrons, were produced at the etched surface, resulting in a shift of the Fermi level near to the conduction band. This leads to the reduction in contact resistivity through the decrease of the Schottky barrier for the conduction of electrons.

Nonalloyed transparent ohmic contact of indium tin oxide to p-type Si0.8Ge0.2

“…For the samples annealed under 400¨600 -C ambient, the point defects could be annealed out, releasing electrons, and thus holes are compensated, leading to higher ohmic contact resistance. The behavior of defects induced by plasma or electron bombardment has been widely observed in compound semiconductor, such as GaN [17,18] and SiGe [19,20]. The sample annealed under 500 -C showed lower ohmic contact resistance than the one under 400 -C. It might be explained by the point defects reactivated under 500 -C annealing temperature, causing an increase of hole concentration and hence the contact resistance was reduced.…”

Effects of cap layer on ohmic Ti/Al contacts to Si+ implanted GaN

“…To verify this, a reported successfully Ti/Al metal scheme was chosen due to its low work function [18][19][20][21]. Ti helps to improve the adhesion and reacts easily with N forming a TiN interface often even only after deposition [15].…”

“…It has been demonstrated that induced damage in nitride materials may take various forms, leading to changes in their electrical properties [16]. Previous works reported that surface treatments, and in particular plasmabased etching, can significantly improve the quality of ohmic contacts to n-type GaN [17,18]. Si implantation, as well as plasma etching, produces Nitrogen vacancies on the surface, which is desirable for the improvement of contact resistance.…”

Ohmic Contacts to implanted GaN

“…It has been demonstrated that induced damage in nitride materials may take various forms, leading to changes in their electrical properties [13]. Previous works reported that surface treatments, and in particular plasma-based etching, can significantly improve the quality of ohmic contacts to n-type GaN [14][15]. Si implantation, as well as plasma etching, produces Nitrogen vacancies on the surface, which is desirable for the improvement of contact resistance.…”