Recent Progress in Source/Drain Ohmic Contact with β-Ga2O3

Abstract

β-Ga2O3, with excellent bandgap, breakdown field, and thermal stability properties, is considered to be one of the most promising candidates for power devices including field-effect transistors (FETs) and for other applications such as Schottky barrier diodes (SBDs) and solar-blind ultraviolet photodetectors. Ohmic contact is one of the key steps in the β-Ga2O3 device fabrication process for power applications. Ohmic contact techniques have been developed in recent years, and they are summarized in this review. First, the basic theory of metal–semiconductor contact is introduced. After that, the representative literature related to Ohmic contact with β-Ga2O3 is summarized and analyzed, including the electrical properties, interface microstructure, Ohmic contact formation mechanism, and contact reliability. In addition, the promising alternative schemes, including novel annealing techniques and Au-free contact materials, which are compatible with the CMOS process, are discussed. This review will help our theoretical understanding of Ohmic contact in β-Ga2O3 devices as well as the development trends of Ohmic contact schemes.

A Review of β-Ga2O3 Power Diodes

“…; graphite also forms Schottky contacts with β-Ga 2 O 3 . Among these, Ni is widely used, due to its low cost and ability to form excellent Schottky contacts with β-Ga 2 O 3 [110][111][112][113]. At present, Ga2O3 materials still lack effective p-type doping, and resea applications are basically n-Ga2O3, typically doping with elements like Si and Sn with range of 10 15 to 10 19 cm −3 in concentration.…”

“…; graphite also fo Schottky contacts with β-Ga2O3. Among these, Ni is widely used, due to its low cost ability to form excellent Schottky contacts with β-Ga2O3 [110][111][112][113]. [108].…”

“…Currently, almost all Ga 2 O 3 devices use Ti as the ohmic contact and deposit Au as a protective layer to avoid oxidation. The ohmic contacts can be effectively formed by heavy doping, plasma treatment, and post-annealing treatment [110][111][112][113]. In 2012, Higashiwaki et al [130] first reported a field-effect transistor based on β-Ga 2 O 3 , utilizing Ti/Au ohmic contacts, and highlighted the necessity of Reactive Ion Etching (RIE) processing for establishing ohmic contacts.…”

Resistor-to-Schottky barrier analytical model for ohmic contact test structures

“…For example, beta-phase gallium oxide (β-Ga 2 O 3 ) has the potential to significantly increase the efficiency of high-power electronics [15,16]. Low contact resistance for this material has been achieved using heavily doped semiconductors [17], adding an intermediate semiconductor layer between the metal and the β-Ga 2 O 3 substrate [18], or selection of different electrode metals [19][20][21][22]. Once again, high-accuracy analytical models are required to assist development of better contacts to emerging 2D and wide bandgap semiconductors.…”

Research on the carrier transmission distance of a-Ga2O3 solar-blind photodetector

“…[4] In recent years, several review articles have been summarized for crystalline Ga2O3 UV photodetectors (PDs). [5][6][7][8] Compared with β-phase Ga2O3, amorphous gallium oxide (a-Ga2O3) has received more and more attention from researchers due to its high breakdown field strength, low-temperature preparation, and other advantages. Magnetron sputtering, as a well-developed thin-film deposition technology, has the advantages of simple equipment, low deposition temperature, high deposition rate, good adhesion, and good uniformity, and is suitable for large-area deposition, and has been widely used in industry.…”