April 22 - 26, 2024
Seattle, Washington
May 7 - 9, 2024 (Virtual)

Event Supporters

2024 MRS Spring Meeting
EL04.09.01

Investigation of Temperature-dependent Hysteresis and Interface Trap Density in E-Beam Evaporated NiOx/β-Ga2O3 p-n Diodes

When and Where

Apr 25, 2024
8:15am - 8:30am
Room 345, Level 3, Summit

Presenter(s)

Co-Author(s)

Bingcheng Da1,Dinusha Herath Mudiyanselage1,Dawei Wang1,Ziyi He1,Houqiang Fu1

Arizona State University1

Abstract

Bingcheng Da1,Dinusha Herath Mudiyanselage1,Dawei Wang1,Ziyi He1,Houqiang Fu1

Arizona State University1
β-Ga<sub>2</sub>O<sub>3</sub>, an ultra-wide bandgap (UWBG) material with a bandgap of 4.9 eV and a high breakdown field of ~8 MV/cm, holds promise for power, optical, and RF electronics. However, due to the absence of p-type Ga<sub>2</sub>O<sub>3</sub>, most demonstrated devices have been unipolar. This limitation is attributed to the lack of shallow acceptors and the presence of holes trapped in localized polarons. To address this, p-NiO<sub>x</sub> has been utilized to create p-n heterojunctions with β-Ga<sub>2</sub>O<sub>3</sub>, resulting in devices such as p-n diodes and junction barrier Schottky (JBS) diodes. While these devices exhibit desirable properties, they also exhibit charge trapping, hysteresis in forward and reverse bias, and induced interface states at the heterojunction. This study aims to comprehensively investigate the temperature-dependent hysteresis and interface trap density in NiO<sub>x</sub>/β-Ga<sub>2</sub>O<sub>3</sub> p-n diodes on (-201) Ga<sub>2</sub>O<sub>3</sub> crystal orientations.<br/>The edge-defined film-fed grown β-Ga<sub>2</sub>O<sub>3</sub> substrates were sourced from Novel Crystal Technology, Inc. (Japan) and had a n-type doping concentration of [Sn] = 5×10<sup>18</sup> cm<sup>−3</sup>, with uniform thickness and polished front sides. Prior to device fabrication, substrate cleaning involved sequential treatments with acetone, isopropyl alcohol (IPA), and deionized (DI) water. Subsequently, electron beam (E-beam) evaporation was used to deposit Ti/Au (20/130 nm) back contacts, followed by rapid thermal annealing at 500 °C in an N<sub>2</sub> environment. Photolithography was employed to define circular areas of 300 µm in diameter for NiO<sub>x</sub> and anode material deposition (Ni/Au, 20/130 nm). Layers of NiO<sub>x</sub> (200 nm) were deposited using e-beam evaporation, and a liftoff process was executed to isolate individual devices. Post-fabrication, devices underwent annealing at 350 °C in an N<sub>2</sub> atmosphere for 1 minute to improve performance by reducing the number of interface states at the NiO<sub>x</sub>/β-Ga<sub>2</sub>O<sub>3</sub> heterojunction.<br/>Preliminary findings indicate hysteresis during forward and reverse bias, but none in C-V measurements. With increasing temperature, forward bias hysteresis decreases, while reverse bias hysteresis remains constant. The experiment covers a voltage range of +3 V to −10 V. Concurrently, capacitance-frequency measurements were conducted to evaluate trap density, which varied between 5×10<sup>11</sup> and 2×10<sup>11</sup> eV<sup>−1</sup>cm<sup>−2</sup> as the temperature ranged from room temperature to 395 K. These results suggest that temperature-dependent interface trap states contribute to the observed hysteresis in the devices. Future investigations will extend to NiO<sub>x</sub>/β-Ga<sub>2</sub>O<sub>3</sub> devices on (010) crystal orientation. Previous studies have indicated distinct electronic properties between (-201) and (010) devices due to crystal anisotropy. This study will provide valuable insights into transport properties of NiO<sub>x</sub>/β-Ga<sub>2</sub>O<sub>3</sub> p-n diodes and pave the path for device optimization by reducing interface trap states.

Symposium Organizers

Hideki Hirayama, RIKEN
Robert Kaplar, Sandia National Laboratories
Sriram Krishnamoorthy, University of California, Santa Barbara
Matteo Meneghini, University of Padova

Symposium Support

Silver
Taiyo Nippon Sanso

Session Chairs

Sriram Krishnamoorthy
Joel Varley

In this Session