Effect of low-temperature-grown GaN cap layer on reduced leakage current of GaN Schottky diodes (original) (raw)
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Ultra-low leakage and high breakdown Schottky diodes fabricated on free-standing GaN substrate
Semiconductor Science and Technology, 2011
Vertical Schottky diodes were fabricated on the bulk GaN substrate with decreasing impurity concentration from N-face to Ga-face. An array of circular Pt Schottky contacts and a full backside Ti/Al/Ni/Au ohmic contact were prepared on the Ga-face and the N-face of the n-GaN substrate, respectively. The Schottky diode exhibits a minimum specific on-state resistance of 1.3 m cm 2 and a maximum breakdown voltage of 600 V, resulting in a figure-ofmerit of 275 MW cm −2 . An ultra-low reverse leakage current density of 3.7 × 10 −4 A cm −2 at reverse bias of 400 V was observed. Temperature-dependent I-V measurements were also carried out to study the forward and reverse transportation mechanisms.
Dislocation-related conduction paths in n-type GaN grown by molecular-beam epitaxy and a mechanism for local suppression of current flow along these paths are analyzed using conductive atomic force microscopy, scanning Auger spectroscopy, and macroscopic current-voltage measurements. Application of an electric field at the GaN surface in an ambient atmospheric environment is shown to lead to local formation of gallium oxide in the immediate vicinity of the conduction paths, resulting in the strong suppression of subsequent current flow. Current-voltage measurements for Schottky diodes in which local conduction paths have been suppressed in this manner exhibit reverse-bias leakage currents reduced by two to four orders of magnitude compared to those in Schottky diodes not subjected to any surface modification process. These results demonstrate that the dislocation-related current leakage paths are the dominant source of leakage current in Schottky contacts to n-type GaN grown by molecular-beam epitaxy, and elucidate the nature of a microscopic process for their suppression.
Analysis of Reverse Leakage Current and Breakdown Voltage in GaN and InGaN/GaN Schottky Barriers
IEEE Transactions on Electron Devices, 2011
A study of the reverse-leakage-current mechanisms in metal-organic-chemical-vapor-deposition (MOCVD)-grown GaN Schottky-barrier diodes is presented. An analysis is carried out of the characteristics of GaN Schottky diodes as well as of diodes with an InGaN surface layer to suppress the reverse leakage current and increase the breakdown voltage. The experimental results of the diodes with InGaN surface layers showed a ~ 40-V breakdown voltage increase and a significant leakage-current reduction under high reverse bias, in comparison with the design with GaN only. Such improvements are attributed to the reduced surface electric field and the increased electron tunneling distance induced by the polarization charges at the InGaN/GaN interface. We also report the effect of a high-pressure (near atmospheric pressure) MOCVD growth technique of the GaN buffer layer to further improve the leakage current and breakdown voltage.
Electrical Characteristics of Au/n-GaN Schottky Junction with a High-k SrTiO3 Insulating Layer
Journal of Nano- and Electronic Physics, 2019
The electrical characteristics of Au/n-GaN Schottky junction (SJ) were improved by a place of high-k strontium titanate (SrTiO3) insulating layer in the middle of Au and n-GaN. The electrical properties of Au/n-GaN SJ and Au/SrTiO3/n-GaN metal/insulator/semiconductor (MIS) junction were explored by current-voltage and capacitance-voltage techniques. The MIS junction displayed an exquisite rectifying nature as compared to the SJ. The series resistance (RS) and shunt resistance (RSh) were found to be 30 Ω, 4.69 10 6 Ω and 250 Ω, 2.12 10 9 Ω for the SJ and MIS junction, respectively. The estimated barrier height (BH) and ideality factors of SJ and MIS junction were 0.67 eV, 1.44 and 0.83 eV, 1.78, respectively. Higher BH was achieved for the MIS junction than the SJ junction, suggesting the BH was effectually changed by the SrTiO3 layer. Also, the ideality factor, BH and series resistance of the SJ and MIS junction were estimated by employing the Cheung's function and compared each other. Observations reveal the ohmic behavior at lower voltage regions and space-charge-limited conduction at higher voltage regions in the forward bias I-V characteristic of the SJ and MIS junctions. Also, the reverse leakage current conduction mechanism of SJ and MIS junctions was explored.
Japanese Journal of Applied Physics, 2006
We have proposed and fabricated a lateral GaN Schottky barrier diode (SBD) that increases the breakdown voltage and decreases the leakage current by the oxidation of a Ni/Au Schottky contact. After an oxidation, the anode current was increased under a high anode bias, whereas the turn-on voltage was slightly increased. The leakage current was considerably decreased to less than 1 nA after the oxidations of 5 and 10 min. A high breakdown voltage of 750 V was measured in the proposed GaN SBD when multiple floating metal rings (FMRs) were used for edge termination and oxidation was employed. We have also measured the reverse recovery waveforms at room temperature and 125 C and the fabricated GaN SBDs show very fast reverse recovery characteristics.
Characterization and modeling of Schottky diodes based on bulk GaN unintentionally doped
HAL (Le Centre pour la Communication Scientifique Directe), 2014
In this paper, we have studied Au/n-GaN Schottky diodes. The substrates are realized on bulk GaN. The current-voltage (I-V) and capacitance-voltage (C-V) of Au/n-GaN structures were investigated at room temperature. The electrical parameters such as saturation current I 0 (1.98 ×10 −7 A), ideality factor n (1.02), barrier height φ bn (0.65 eV) and series resistance Rs (84 Ω) were evaluated from I-V experimental data. The characteristics in these data structures Schottky Au/n-GaN can help to highlight the main conduction mechanisms observed. In addition to the thermionic current present in our structures, the leakage current intervenes too. The barrier height and doping determined from the (C-V) characteristic are of the order of 1.17 eV and 8.16 × 10 16 cm-3 , respectively. The average density of surface states N ss determined set to 1.09 × 10 12 eV-1 cm-2 .
Thin-film GaN Schottky diodes formed by epitaxial lift-off
Applied Physics Letters, 2017
The unique material properties of GaN and related III-N semiconductors, such as a high critical electrical field, large band gap, high saturation electron velocity, good electron mobility, and high thermal conductivity 1,2 , have made GaN and related materials one of the most promising material systems for high-performance optoelectronics as well as next-generation power electronics. Despite the inherent material advantages of GaN and numerous device demonstrations, the actual performance of many lateral GaN devices has fallen short of the ultimate performance expected from consideration of fundamental material parameters. These performance discrepancies, which include effects such as large ideality factors, higher-than-expected reverse saturation currents, and the inability to support avalanche currents in diodes 3 , 4 and the presence of surface-and/or buffer-related effects such as dynamic on-state resistance, current-collapse, and hysteresis in FETs, 5,6 have thus far limited the applications that can be addressed using GaN electronics. The use of lattice-mismatched non-native GaN substrates (driven by the high cost and limited availability of native GaN substrates) also results not only in large dislocation densities but also limited thermal conductance for through-substrate heat removal. 7,8 As is well known, power devices are typically thermally limited 9,10 so that the die size is set by power dissipation and thermal resistance considerations, rather than by current density limitations. Epitaxial lift-off (ELO) processing offers an alternative approach to address these issues.