Characteristics of Al₂O₃/native oxide/n-GaN capacitors by post-metallization annealing

Abstract

This work investigated characteristics of Al 2 O 3 /native oxide/n-GaN MOS capacitors by postmetallization annealing (PMA). A native oxide interlayer which composed of εand γ-Ga 2 O 3 phases (Native oxide) and the reduced amount of one (Reduced) on n-GaN were prepared by cleaning only a sulfuric acid peroxide mixture (SPM) and both SPM and buffered hydrofluoric acid, respectively. The effect of trimethylaluminum precursor on removal of a native oxide layer was not observed during Al 2 O 3 deposition using atomic layer deposition. An as-grown capacitor (Native oxide) exhibited a small flatband voltage (V fb ) hysteresis of ∼30 mV and a large frequency dispersion, suggesting that the initial growth of the Al 2 O 3 resulted in the formation of electrical defects on the GaN surface. Both the V fb hysteresis and frequency dispersion were drastically improved by PMA of the device at 300 °C. The positive fixed charge values (Q IL ) estimated from the relationships between capacitance equivalent thickness and V fb were +6.1×10 12 and +0.4-1.0×10 12 cm −2 for as-grown and PMA-processed capacitors in the PMA temperature range of 300 °C-600 °C, respectively. The interface state density (D it ) determined using a conductance method was also significantly reduced (by an order of magnitude) after PMA processing at 300 °C. These trends in the Q IL and D it data were observed in both the Native oxide and Reduced capacitors, indicating that this interlayer does not greatly affect fixed charge generation at the Al 2 O 3 /native oxide and Al 2 O 3 /modified native oxide interfaces. As a result, two types of treatments result in insignificant difference in the electrical properties of the capacitors.

Improved operation stability of in situ AlSiO dielectric grown on (000–1) N-polar GaN by MOCVD

“…The improved interfacial properties suggests that annealing resulted in the reduction of surface/interface defects or dangling bonds similar to the previously observed trap reduction at the interface between Al 2 O 3 and Ga-polar GaN. [31][32][33] Further investigations will be pursued in the future to provide more physical understanding on the impact of annealing on the interface between AlSiO and N-polar GaN. It is noted that annealing at 370 °C resulted in little additional improvement in the density of trapped charge and near-interface traps with respect to annealing at 320 °C.…”

Comparison of Hydrogen-Induced Oxide Charges Among GaN Metal-Oxide-Semiconductor Capacitors with Al2O3, HfO2, or Hf0.57Si0.43Ox Gate Dielectrics

“…For samples A1, A2, A3, B2, and C2 in Table I, the electrical characteristics of devices fabricated using the same process have been described in detail in our previous papers; 14,17,18 the data are summarized in Table II. As shown in Table II, the devices used in the present study exhibit various electrical characteristics.…”

Surface Preconditioning and Postmetallization Anneal Improving Interface Properties and Vth Stability under Positive Gate Bias Stress in AlGaN/GaN MIS‐HEMTs

“…[14][15][16][17] Therefore, the minimization of trap states at the interface is a critical issue for GaN-based MIS-HEMTs. Although a reduction of the interface trap density (D it ) has been reported after various surface treatments and postdeposition annealing, [6,[18][19][20][21][22][23][24] still few reports have dealt with the effects of surface and postdeposition treatments in terms of D it and their related implications on V th stability during forward gate bias stress conditions.…”