Abstract
The literature on polar Gallium Nitride (GaN) surfaces, surface treatments and gate dielectrics relevant to metal oxide semiconductor devices is reviewed. The significance of the GaN growth technique and growth parameters on the properties of GaN epilayers, the ability to modify GaN surface properties using in situ and ex situ processes and progress on the understanding and performance of GaN metal oxide semiconductor (MOS) devices are presented and discussed. Although a reasonably consistent picture is emerging from focused studies on issues covered in each of these topics, future research can achieve a better understanding of the critical oxide-semiconductor interface by probing the connections between these topics. The challenges in analyzing defect concentrations and energies in GaN MOS gate stacks are discussed. Promising gate dielectric deposition techniques such as atomic layer deposition, which is already accepted by the semiconductor industry for silicon CMOS device fabrication, coupled with more advanced physical and electrical characterization methods will likely accelerate the pace of learning required to develop future GaN-based MOS technology.
Highlights
Gallium nitride (GaN) is a wide bandgap (3.4 eV) semiconducting material with a high breakdown voltage and, as such, is ideal for high frequency, high power and high temperature applications [1].The use of GaN in commercial electronic devices outside the LED market has until recently beenMaterials 2012, 5 somewhat limited
The results are in agreement with experiment, for example see reference [68] for the Ga rich (000 1 ) case, and suggest that the microscopic origin of the Fermi-level pinning on GaN surfaces occurs via formation of either Ga dangling bonds at moderate Ga/N ratios or
Report that UV/O3 and wet chemical treatments based on HF and HCl are very effective in removing surface C and reducing the native oxide thickness on GaN but it further suggests that high vacuum in situ cleaning methods are needed to obtain an oxygen free air exposed GaN surface
Summary
Gallium nitride (GaN) is a wide bandgap (3.4 eV) semiconducting material with a high breakdown voltage and, as such, is ideal for high frequency, high power and high temperature applications [1]. This results in high carrier concentration in a narrow region (quantum well) parallel to the surface under the AlGaN layer. To date GaN HEMTs have primarily been used in radio frequency (RF) amplifiers for base stations and military applications In such RF devices there is a need to reduce gate leakage current, High-κ insulators/oxides on the AlGaN/GaN HEMT structures have been used to address this problem—this aspect will be discussed later in this review.
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