Mg-compensation effect in GaN buffer layer for AlGaN/GaN high-electron-mobility transistors grown on 4H-SiC substrate

Abstract

The present study investigated the Mg doping effect in the gallium nitride (GaN) buffer layers (BLs) of AlGaN/GaN high-electron-mobility transistor (HEMT) structures grown on semi-insulating 4H-SiC substrates by metal organic chemical vapor deposition. When the Mg concentration was increased from 3 × 1017 to 8 × 1018 cm−3, the crystal quality slightly deteriorated, whereas electrical properties were significantly changed. The buffer leakage increased approximately 50 times from 0.77 to 39.2 nA at −50 V with the Mg doping concentration. The Mg-compensation effect and electron trapping effect were observed at Mg concentration of 3 × 1017 and 8 × 1018 cm−3, respectively, which were confirmed by an isolation leakage current test and low-temperature photoluminescence. When the BL was compensated, the two-dimensional electron gas (2DEG) mobility and sheet carrier concentration of the HEMTs were 1560 cm2 V−1 s−1 and 5.06 × 1012 cm−2, respectively. As a result, Mg-doped GaN BLs were demonstrated as a candidates of semi-insulating BLs for AlGaN/GaN HEMT.

Vertical GaN-on-GaN Schottky Diodes as α-Particle Radiation Sensors

“…To understand the physical significance of the change in CM The activation energy was also extracted in all voltage zones [55,56]. The extracted E a of 0.4 eV corresponds to the presence of Mg ions in the DL [59,60]. The activation of N-vacancies [61] (E a = −1.67 eV) with an increase in temperature resulted in the trapping of tunneling electrons and changing the CM from TFE to TE in Zone-II of both SBDs.…”

Mg Doping of N-Polar, In-Rich InAlN

“…This was reflected by the Hall-method-determined free electron concentration of ~10 19 cm 3 in an undoped, MOCVD-grown In 0.57 Al 0.43 N reported by us [ 7 ], or in InN even after p-type doping [ 9 ]. Still, the compensation of residual donors in III-N buffer layers using relatively easily ionized Mg acceptors (when compared with C or Fe acceptors) may be the most viable method, as was already demonstrated in AlGaN/GaN transistors [ 10 ]. In MOCVD, Mg-doping is typically achieved by adding the bis(cyclopentadienyl) magnesium Cp 2 Mg precursor flow [ 9 , 10 , 11 , 12 , 13 ].…”

“…Still, the compensation of residual donors in III-N buffer layers using relatively easily ionized Mg acceptors (when compared with C or Fe acceptors) may be the most viable method, as was already demonstrated in AlGaN/GaN transistors [ 10 ]. In MOCVD, Mg-doping is typically achieved by adding the bis(cyclopentadienyl) magnesium Cp 2 Mg precursor flow [ 9 , 10 , 11 , 12 , 13 ]. In GaN layers, when a Cp 2 Mg/trimethylgalium (TMG) flow ratio between 0.6 and 1.6 × 10 −3 is used, the Mg concentration reaches approximately 2 × 10 19 cm −3 [ 11 , 12 ].…”

“…In GaN layers, when a Cp 2 Mg/trimethylgalium (TMG) flow ratio between 0.6 and 1.6 × 10 −3 is used, the Mg concentration reaches approximately 2 × 10 19 cm −3 [ 11 , 12 ]. In such cases, as the Mg-related acceptor level is 0.25 eV above the valence band, providing an ionization rate of approximately 4 % at RT, the hole concentrations are ~10 17 cm −3 [ 10 , 11 , 12 ]. In other words, GaN can easily become semi-insulating or show p-type conduction if virgin GaN is only lightly n-type doped (electron concentration ≤10 17 cm −3 ).…”

“…Mg doping also significantly influences the optical properties of III-N layers [ 9 , 10 ]. The low-temperature photoluminiscence (PL) spectra of GaN showed several Mg-related peaks within the bandgap with a rising intensity depending on the Cp 2 Mg flow.…”