Highly resistive GaN layers formed by ion implantation of Zn along the c axis

Abstract

Highly resistive layers are formed by the implantation of Zn ion along the c axis of GaN and AlGaN/GaN epitaxial layers. Heavy ions such as Zn have been desirable for the formation of highly resistive layers, because ions effectively transferred their energy to the crystal atoms rather than the electrons in GaN. A sheet resistance Rs as high as 3.8×1011 Ω/sq was obtained on GaN layers after the ion implantation. Rs increased up to 2.2×1013 Ω/sq after the annealing at 500 °C for 300 s in an N2 atmosphere. The thermal activation energy Er for this sample was 0.67 eV. It was found that the experimental data in current–voltage characteristics were fitted to the equation included the Poole–Frenkel current and resistive (ohmic) current. The difference of Rs between the as-implanted and 500 °C annealed samples was due to the Poole–Frenkel current. The Poole–Frenkel current overcame the resistive one, and dominated the current mechanism in the case of the samples annealed at 200 °C or less. On the other hand, for the samples annealed at 500 °C, the current was only resistive. Both Rs and Er decreased as the annealing temperature increased above 500 °C. Furthermore this implantation method was applied to the device isolation of AlGaN/GaN high electron mobility transistors (HEMTs). The high Rs of 5.9×1011 Ω/sq was observed for AlGaN/GaN structures as well as GaN layers which were not annealed. The HEMTs with a gate length of 1 μm had a high drain current of over 1 A/mm at the gate voltage of 1 V and a pinch off voltage of −7 V without a harmful leakage current.

Dynamic annealing in III-nitrides under ion bombardment

“…[1][2][3][4] Recently, ion-bombardment-produced defects have also been studied in InGaN, AlGaN, and AlN. [5][6][7][8][9][10][11][12][13][14] It has been shown that an increase in In content strongly suppresses dynamic annealing processes ͑i.e., defect migration and interaction processes͒ and enhances the buildup of stable lattice disorder. 8 Interestingly, an increase in Al concentration in the AlGaN alloy has the opposite effect on the efficiency of dynamic annealing, increasing material resistance to ion-beaminduced disordering.…”

Oxygen Ion Implantation Isolation Planar Process for AlGaN/GaN HEMTs

“…Implantation isolation have been studied in pure GaN or AlGaN material using H + , He + , N + , F + , Mg + , Ar + , and Zn + ions [2]- [8]. The O + ion implant isolation was also investigated on AlGaAs [9], InAlN [10], and GaN (n-type doping)/GaN materials [11] to study the isolation quality, and P/He, Ar + , and N + ions have been employed in AlGaN/GaN HEMTs [12]- [14].…”

AlGaN Channel HEMT with Extremely High Breakdown Voltage

“…After removing the SiN cap layer in a HF solution, source/drain ohmic contacts were formed by Ti/Al metallization and subsequent rapid thermal annealing at 600 O C for 2 min in an environment of flowing nitrogen. Then device isolation was performed by Zn ion implantation 12 and Ni/Au Schottky gate contact was formed. The fabrication of HEMTs was completed by depositing a SiN dielectric film using catalytic chemical vapor deposition [13][14][15] and subsequent formation of a Ni/Au field plate which was connected to the gate contact at an electrode pad.…”