High breakdown voltage in AlGaN/GaN HEMTs using AlGaN/GaN/AlGaN quantum-well electron-blocking layers
© Lee et al.; licensee Springer. 2014
Received: 6 June 2014
Accepted: 19 August 2014
Published: 27 August 2014
In this paper, we numerically study an enhancement of breakdown voltage in AlGaN/GaN high-electron-mobility transistors (HEMTs) by using the AlGaN/GaN/AlGaN quantum-well (QW) electron-blocking layer (EBL) structure. This concept is based on the superior confinement of two-dimensional electron gases (2-DEGs) provided by the QW EBL, resulting in a significant improvement of breakdown voltage and a remarkable suppression of spilling electrons. The electron mobility of 2-DEG is hence enhanced as well. The dependence of thickness and composition of QW EBL on the device breakdown is also evaluated and discussed.
KeywordsAlGaN/GaN HEMT 2-DEG Breakdown voltage
GaN-based high-electron-mobility transistors (HEMTs) have attracted considerable interests for the high-speed and high-power-switching applications because of their outstanding electronic properties. The high sheet-carrier density of the two-dimensional electron-gas (2-DEG)[1, 2] and large critical breakdown electric field[3, 4] allow the fabricated HEMT devices with unprecedented high drain current density and large breakdown voltage, which are essential for the important applications of power devices[5–9]. However, the high sheet electron density inherently in GaN-based HEMTs will inevitably induce the spillover of transport electrons at high-drain-voltage conditions, and that becomes a growing issue. In general, the confinement of transport electrons to the bottom side of the device is insufficient in the conventional AlGaN/GaN HEMT, due mainly to the insufficient potential height provided by the GaN buffer layer underneath. Consequently, transport electrons supposed to be confined within the 2-DEG channel would easily spill or leak into the buffer layer, causing a rapid increase of subthreshold drain leakage currents, accelerating the device breakdown. The above-mentioned phenomenon is often interpreted as the ‘punchthrough effect,’ hindering the further applications of GaN-based HEMTs. Therefore, methods improving the confinement of transport electrons within the channel layer and alleviating the punchthrough effect are necessary. Over the years, several approaches, such as the introduction of p-type doping to the GaN buffer layer[10–12] and the use of AlGaN/GaN/AlGaN double-heterojunction HEMTs[13–15], have been reported to enhance the breakdown voltage of GaN-based HEMTs. The basic principle is to raise the conduction band of the GaN buffer layer, and thus generates a deeper and narrower potential well for the better confinement of 2-DEG.
In this work, we present an improved bottom confinement of 2-DEG by introducing the AlGaN/GaN/AlGaN quantum-well (QW) electron-blocking layer (EBL) structure. It is shown that the large electric field induced at the interfaces of AlGaN/GaN/AlGaN QW EBL effectively depletes the spilling electrons toward the 2-DEG channel. As compared to previous approaches, the subthreshold drain leakage current becomes less sensitive to the drain voltage (Vds), and that postpones the HEMT breakdown. Meanwhile, our proposed structure not only exhibits the highest electron mobility among other compared HEMT devices but also allows a great tolerance for epitaxial imperfections during the device fabrication. As a result, we conclude that the proposed AlGaN/GaN/AlGaN QW EBL HEMT is viable and highly promising for the high-speed and high-power-switching applications.
Specifically, to calculate the impact ionization in the GaN wurtzite structure, the values of coefficients αn,p and Ecritn,p were set to be 2.60 × 108 cm−1 and 3.42 × 107 V cm−1 for electrons, and 4.98 × 106 cm−1 and 1.95 × 107 V cm−1 for holes, respectively.
Results and discussion
In conclusion, we propose a novel AlGaN/GaN/AlGaN QW EBL structure to alleviate the punchthrough effect that is generally observed on the conventional AlGaN/GaN HEMT. The introduction of AlGaN/GaN/AlGaN QW EBL leads to a better confinement of transport electrons into the 2-DEG channel, resulting in a reduction of subthreshold drain leakage current and a postponement of device breakdown. The large electric field induced at the interfaces of AlGaN/GaN/AlGaN QW EBL, which effectively depletes the spilling electrons toward the 2-DEG channel, is mainly responsible for the improved performances.
The authors gratefully acknowledge financial support from the National Science Council of the Republic of China (ROC) in Taiwan (contract no. NSC–100–2112–M–003–006–MY3), from the Bureau of Energy, Ministry of Economic Affairs in Taiwan, and from the Ministry of Science and Technology in Taiwan (contract no. MOST 103–2112–M–003–008–MY3).
- Mustafa F, Hashim AM: Generalized 3D transverse magnetic mode method for analysis of interaction between drifting plasma waves in 2DEG-structured semiconductors and electromagnetic space harmonic waves. Prog Electromagn Res 2010, 102: 315–335.View ArticleGoogle Scholar
- Park PS, Nath DN, Krishnamoorthy S, Rajan S: Electron gas dimensionality engineering in AlGaN/GaN high electron mobility transistors using polarization. Appl Phys Lett 2012, 100: 063507.View ArticleGoogle Scholar
- Saito W, Takada Y, Kuraguchi M, Tsuda K, Omura I, Ogura T, Ohashi H: High breakdown voltage AlGaN-GaN power-HEMT design and high current density switching behavior. IEEE Trans Electron Devices 2003, 50: 2528–2531.View ArticleGoogle Scholar
- Saito W, Omura I, Ogura T, Ohashi H: Theoretical limit estimation of lateral wide band-gap semiconductor power-switching device. Solid State Electron 2004, 48: 1555–1562.View ArticleGoogle Scholar
- Cho E, Brunner F, Zhytnytska R, Kotara P, Würfl J, Weyers M: Enhancement of channel conductivity in AlGaN/GaN heterostructure field effect transistors by AlGaN:Si back barrier. Appl Phys Lett 2011, 99: 103505.View ArticleGoogle Scholar
- Bahat-Treidel E, Brunner F, Hilt O, Cho E, Wurfl J, Trankle G: AlGaN/GaN/GaN:C back-barrier HFETs with breakdown voltage of over 1 kV and low RON × A. IEEE Trans Electron Devices 2010, 57: 3050–3058.View ArticleGoogle Scholar
- Xu Y, Guo Y, Xia L, Wu Y: An support vector regression based nonlinear modeling method for SiC MESFET. Prog Electromagn Res 2008, 2: 103–114.View ArticleGoogle Scholar
- Lee YJ, Yang ZP, Lo FY, Siao JJ, Xie ZH, Chuang YL, Lin TY, Sheu JK: Slanted n-ZnO/p-GaN nanorod arrays light-emitting diodes grown by oblique-angle deposition. APL Mater 2014, 2: 056101.View ArticleGoogle Scholar
- Sun HH, Guo FY, Li DY, Wang L, Wang DB, Zhao LC: Intersubband absorption properties of high Al content Al(x)Ga(1 − x)N/GaN multiple quantum wells grown with different interlayers by metal organic chemical vapor deposition. Nanoscale Res Lett 2012, 7: 649.View ArticleGoogle Scholar
- Brunner F, Bahat-Treidel E, Cho M, Netzel C, Hilt O, Würfl J, Weyers M: Comparative study of buffer designs for high breakdown voltage AlGaNGaN HFETs. Phys Status Solidi C 2011, 8: 2427–2429.View ArticleGoogle Scholar
- Sadahiro K, Yoshihiro S, Hitoshi S, Iwami M, Seikoh Y: C-doped GaN buffer layers with high breakdown voltages for high-power operation AlGaN/GaN HFETs on 4-in Si substrates by MOVPE. J Cryst Growth 2007, 298: 831–834.View ArticleGoogle Scholar
- Choi YC, Pophristic M, Peres B, Cha H-Y, Spencer MG, Eastman LF: High breakdown voltage C-doped GaN-on-sapphire HFETs with a low specific on-resistance. Semicond Sci Technol 2007, 22: 517–521.View ArticleGoogle Scholar
- Bahat-Treidel E, Hilt O, Brunner F, Wurfl J, Trankle G: Punchthrough-voltage enhancement of AlGaN/GaN HEMTs using AlGaN double-heterojunction confinement. IEEE Trans Electron Devices 2008, 55: 3354–3358.View ArticleGoogle Scholar
- Xu PQ, Jiang Y, Chen Y, Ma ZG, Wang XL, Deng Z, Li Y, Jia HQ, Wang WX, Chen H: Analyses of 2-DEG characteristics in GaN HEMT with AlN/GaN super-lattice as barrier layer grown by MOCVD. Nanoscale Res Lett 2012, 7: 141.View ArticleGoogle Scholar
- Bahat-Treidel E, Hilt O, Brunner F, Sidorov V, Wurfl J, Trankle G: AlGaN/GaN/AlGaN DH-HEMTs breakdown voltage enhancement using multiple grating field plates (MGFPs). IEEE Trans Electron Devices 2010, 57: 1208–1216.View ArticleGoogle Scholar
- Brown GF, Ager JW, Walukiewicz W, Wu J: Finite element simulations of compositionally graded InGaN solar cells. Sol Energ Mat Sol C 2010, 94: 478–483.View ArticleGoogle Scholar
- Bergman L, Chen X, McIlroy D, Davis RF: Probing the AlxGa1-xN spatial alloy fluctuation via UV-photoluminescence and Raman at submicron scale. Appl Phys Lett 2002, 81: 4186–4188.View ArticleGoogle Scholar
- Yao YC, Tsai MT, Huang CY, Lin TY, Sheu JK, Lee YJ: Efficient collection of photogenerated carriers by Inserting double tunnel junctions in III-nitride p-i-n solar cells. Appl Phys Lett 2013, 103: 193503.View ArticleGoogle Scholar
- Kladko V, Kuchuk A, Lytvyn P, Yefanov O, Safriuk N, Belyaev A, Mazur YI, DeCuir EA Jr, Ware ME, Salamo GJ: Substrate effects on the strain relaxation in GaN/AlN short-period superlattices. Nanoscale Res Lett 2012, 7: 289.View ArticleGoogle Scholar
- Emami SD, Hajireza P, Abd-Rahman F, Abdul-Rashid HA, Ahmad H, Harun SW: Wide-band hybrid amplifier operating in S-band region. Prog Electromagn Res 2010, 102: 301–313.View ArticleGoogle Scholar
- Ambacher O, Foutz B, Smart J, Shealy JR, Weimann NG: Two dimensional electron gases induced by spontaneous and piezoelectric polarization in undoped and doped AlGaN/GaN heterostructures. J Appl Phys 2000, 87: 334–344.View ArticleGoogle Scholar
- Domen K, Horino K, Kuramata A, Tanahashi T: Analysis of polarization anisotropy along the c axis in the photoluminescence of wurtzite GaN. Appl Phys Lett 1997, 71: 1996–1998.View ArticleGoogle Scholar
- Rau B, Waltereit P, Brandt O, Ramsteiner M, Ploog KH, Puls J, Henneberger F: In-plane polarization anisotropy of the spontaneous emission of M-plane GaN/(Al, Ga)N quantum wells. Appl Phys Lett 2000, 77: 3343–3345.View ArticleGoogle Scholar
- Hu WD, Chen XS, Quan ZJ, Zhang XM, Huang Y, Xia CS, Lu W, Ye PD: Simulation and optimization of GaN-based metal-oxide-semiconductor high-electron-mobility-transistor using field-dependent drift velocity model. J Appl Phys 2007, 102: 034502–1-034502–7.Google Scholar
- Oubram O, Gaggero-Sager LM, Bassam A, Luna Acosta GA: Transport and electronic properties of two dimensional electron gas in delta-migfet in GaAs. Prog Electromagn Res 2010, 110: 59–80.View ArticleGoogle Scholar
- Maeda N, Saitoh T, Tsubaki K, Nishida T, Kobayashi N: Two-dimensional electron gas transport properties in AlGaN/GaN single- and double-heterostructure field effect transistors. Mater Sci Eng B 2001, 82: 232–237.View ArticleGoogle Scholar
- Maeda N, Saitoh T, Tsubaki K, Nishida T, Kobayashi N: Enhanced effect of polarization on electron transport properties in AlGaN/GaN double-heterostructure field-effect transistors. Appl Phys Lett 2000, 76: 3118–3120.View ArticleGoogle Scholar
- Acar S, Lisesivdin SB, Kasap M, Ozcelik S, Ozbay E: Determination of two-dimensional electron and hole gas carriers in AlGaN/GaN/AlN heterostructures grown by metal organic chemical vapor deposition. Thin Solid Films 2008, 516: 2041–2044.View ArticleGoogle Scholar
- Chaibi M, Fernande T, Mimouni A, Rodriguez-Tellez J, Tazon A, Mediavilla Sanchez A: Nonlinear modeling of trapping and thermal effects on GaAs and GaN MESFET/HEMT devices. Prog Electromagn Res 2012, 124: 163–186.View ArticleGoogle Scholar
- Sang L, Schutt-Aine JE: An improved nonlinear current model for GaN HEMT high power amplifier with large gate periphery. J Electromagnet Wave 2012, 26: 284–293.View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.