Controlling the interface charge density in GaN-based metal-oxide-semiconductor heterostructures by plasma oxidation of metal layers

Abstract

Articles you may be interested inUltraviolet GaN photodetectors on Si via oxide buffer heterostructures with integrated short period oxide-based distributed Bragg reflectors and leakage suppressing metal-oxide-semiconductor contacts J. Appl. Phys. 116, 083108 (2014) In recent years, investigating and engineering the oxide-semiconductor interface in GaN-based devices has come into focus. This has been driven by a large effort to increase the gate robustness and to obtain enhancement mode transistors. Since it has been shown that deep interface states act as fixed interface charge in the typical transistor operating regime, it appears desirable to intentionally incorporate negative interface charge, and thus, to allow for a positive shift in threshold voltage of transistors to realise enhancement mode behaviour. A rather new approach to obtain such negative charge is the plasma-oxidation of thin metal layers. In this study, we present transmission electron microscopy and energy dispersive X-ray spectroscopy analysis as well as electrical data for Al-, Ti-, and Zr-based thin oxide films on a GaN-based heterostructure. It is shown that the plasmaoxidised layers have a polycrystalline morphology. An interfacial amorphous oxide layer is only detectable in the case of Zr. In addition, all films exhibit net negative charge with varying densities. The Zr layer is providing a negative interface charge density of more than 1 Â 10 13 cm -2 allowing to considerably shift the threshold voltage to more positive values. V C 2015 AIP Publishing LLC.

Design and simulation of high-breakdown-voltage GaN-based vertical field-effect transistor with interfacial charge engineering

“…The negative fixed charge exists at the oxide=GaN interface and its density magnitude (∼10 13 cm −2 ) could be equal to the total charge dose in the buffer layer. 12,14,20,21) The Al 0.23 -Ga 0.77 N barrier layer, GaN channel, and n-GaN buffer layer are 15 nm, 25 nm, and 20 µm, respectively. Moreover, p-GaN current-blocking layers (p-CBL) are connected to the source, and related structure-specific parameters are listed in Table I.…”

“…An AlGaN=GaN high-electron-mobility transistor (HEMT) with a high-density interfacial polarization charge has been obtained and studied extensively over the past years. 20,21) Besides, Hung et al have deeply investigated normally-off GaN metal-insulator-semiconductor HEMTs (MISHEMTs) using a positive or negative Al 2 O 3 =GaN interfacial charge. 22,23) Therefore, utilizing an interfacial charge should not be regarded as unreliable.…”

“…12,14,21,24) The challenge in this device fabrication is how to control the fixed charge density at the Al 2 O 3 =GaN interface. Recently, numerous works about controlling the interface charge density in GaN MOSFETs have been carried out by Hahn et al 20) Moreover, Buckley et al pointed out that, when the temperature of deposition varies from 150 to 350 °C, the negative fixed charge at the Al 2 O 3 =SiO 2 interface increases almost linearly from 2 × 10 12 to 8 × 10 12 cm −2 . 11) Their achievements could inspire us to realize the control of charge density by using a suitable growth temperature with good etching method and pretreatment for deposition.…”