Abstract
Magnetron sputter epitaxy (MSE) offers several advantages compared to alternative GaN epitaxy growth methods, including mature sputtering technology, the possibility for very large area deposition, and low-temperature growth of high-quality electronic-grade GaN. In this article, we review the basics of reactive sputtering for MSE growth of GaN using a liquid Ga target. Various target biasing schemes are discussed, including direct current (DC), radio frequency (RF), pulsed DC, and high-power impulse magnetron sputtering (HiPIMS). Examples are given for MSE-grown GaN thin films with material quality comparable to those grown using alternative methods such as molecular-beam epitaxy (MBE), metal–organic chemical vapor deposition (MOCVD), and hydride vapor phase epitaxy (HVPE). In addition, successful GaN doping and the fabrication of practical devices have been demonstrated. Beyond the planar thin film form, MSE-grown GaN nanorods have also been demonstrated through self-assembled and selective area growth (SAG) method. With better understanding in process physics and improvements in material quality, MSE is expected to become an important technology for the growth of GaN.
Highlights
For three decades, III-nitride semiconductors including GaN, InN, AlN, and their alloys have been a subject of intensive research and development activity, resulting in the maturing of the material system and widespread adoption of III-nitride-based devices
Another issue related to liquid Ga target for sputtering is the formation of gas bubbles inside the target
We have reviewed the progress made in Magnetron sputter epitaxy (MSE) growth of GaN thin film and
Summary
III-nitride semiconductors including GaN, InN, AlN, and their alloys have been a subject of intensive research and development activity, resulting in the maturing of the material system and widespread adoption of III-nitride-based devices. MOCVD requires high growth temperature in order to enable the pyrolysis of the ammonia gas into active nitrogen species. This requirement results in limited substrate selection, an upper limit for material doping, and low indium incorporation due to the phase separation in ternary and quaternary systems [4]. A novel growth GaN film method using high-power impulse magnetron sputtering (HiPIMS) has been demonstrated, with the potential to improve GaN material quality [10]. A more recent progress shows the possibility of using MSE to produce high-quality GaN nanorods on various cost-effective and functional substrates [15,16,17], allowing for the fabrication of novel devices.
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