Abstract
The properties of metal-oxide semiconductor (MOS) capacitors with different chemical treatments have been examined in this study. A MOS capacitor consists of an Al2O3/n-GaN/AlN buffer/Si substrate. Four chemical treatments, containing organic solvents, oxygen plasma and BCl3 plasma, dilute acidic and alkali solvents, and hydrofluoric acid, were used to reduce the metal ions, native oxides, and organic contaminants. The n-GaN surface was treated with these chemical treatments before Al2O3 was grown on the treated n-GaN surface to reduce the interface state trap density (Dit). The value of Dit was calculated using the capacitance–voltage curve at 1 MHz. The Dit of a u-GaN surface was modified using various solutions, which further influenced the contact properties of GaN.
Highlights
Surface cleaning treatments are the foundation of a semiconductor device fabrication process [1,2].Surface cleaning significantly affects the epitaxial defects [2], metal contact resistance/stability [3], and overall device quality of GaN-based devices [4]
The metal-oxide semiconductor (MOS) capacitor was grown on silicon
The contact characteristics of Ti/Al/Ti/Au deposited on the GaN were evaluated by circular transmission line model (CTLM)
Summary
Surface cleaning treatments are the foundation of a semiconductor device fabrication process [1,2]. A surface treatment improves the device performance and enhances the ohmic contact characteristics of GaN with metals [3]. Surface treatments have been proposed to improve the ohmic contact properties between a low work function metal contact and a GaN or AlGaN surface. The metal-oxide-semiconductor HEMTs(MOS-HEMTs) structure using different dielectrics material causes different device performance of MOS-HEMTs, such as different C–V characteristics, specific resistance (Ron ), breakdown voltage, Dit value, saturation drain current of the devices [7]. The Al2 O3 used for MOS-HEMTs improve the basic electronic properties and show low leakage current and high breakdown voltage. Four chemical pretreatments were used for MOS capacitors before atomic layer deposition (ALD) of Al2 O3 to modify the surface quality. The characteristics of MOS capacitors and the ohmic contact characteristics of GaN with the four chemical treatments are discussed
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