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Identification of the primary compensating defect level responsible for determining blocking voltage of vertical GaN power diodes

Applied Physics Letters

King, Michael P.; Kaplar, Robert J.; Dickerson, Jeramy; Lee, Stephen R.; Allerman, Andrew A.; Crawford, Mary H.; Marinella, Matthew; Flicker, Jack D.; Fleming, R.M.; Kizilyalli, I.C.; Aktas, O.; Armstrong, Andrew A.

Electrical performance and characterization of deep levels in vertical GaN P-i-N diodes grown on low threading dislocation density (∼104 - 106cm-2) bulk GaN substrates are investigated. The lightly doped n drift region of these devices is observed to be highly compensated by several prominent deep levels detected using deep level optical spectroscopy at Ec-2.13, 2.92, and 3.2 eV. A combination of steady-state photocapacitance and lighted capacitance-voltage profiling indicates the concentrations of these deep levels to be Nt = 3 × 1012, 2 × 1015, and 5 × 1014cm-3, respectively. The Ec-2.92 eV level is observed to be the primary compensating defect in as-grown n-type metal-organic chemical vapor deposition GaN, indicating this level acts as a limiting factor for achieving controllably low doping. The device blocking voltage should increase if compensating defects reduce the free carrier concentration of the n drift region. Understanding the incorporation of as-grown and native defects in thick n-GaN is essential for enabling large VBD in the next-generation wide-bandgap power semiconductor devices. Thus, controlling the as-grown defects induced by epitaxial growth conditions is critical to achieve blocking voltage capability above 5 kV.

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TYPE Journal Article YEAR 2016
DOIOSTIScopus

An AlN/Al0.85Ga0.15N high electron mobility transistor with a regrown ohmic contact

Device Research Conference - Conference Digest, DRC

Baca, Albert G.; Armstrong, Andrew A.; Allerman, Andrew A.; Douglas, Erica A.; Sanchez, Carlos A.; King, Michael P.; Coltrin, Michael E.; Nordquist, Christopher D.; Fortune, Torben; Kaplar, Robert J.

The performance and efficiency of power devices depends on both high breakdown voltage and low on-state resistance. For semiconductor devices, the critical electric field (EC) affecting breakdown scales approximately as Eg25 [1], making the wide bandgap semiconductor materials logical candidates for high voltage power electronics devices. In particular, AlGaN alloys approaching AlN with its 6.2 eV bandgap have an estimated EC approaching 5x that of GaN. This factor makes AlN/AlGaN high election mobility transistors (HEMTs) extremely interesting as candidate power electronic devices. Until now, such devices have been hampered, ostensibly due to the difficulty of making Ohmic contacts to AlGaN alloys with high Al composition. With the use of an AlN barrier etch and regrowth procedure for Ohmic contact formation, we are now able to report on an AlN/AlGaN HEMT with 85% Al.

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TYPE Conference Poster YEAR 2016
OSTIScopus

An AlN/Al0.85Ga0.15N high electron mobility transistor

Applied Physics Letters

Baca, Albert G.; Armstrong, Andrew A.; Allerman, Andrew A.; Douglas, Erica A.; Sanchez, Carlos A.; King, Michael P.; Coltrin, Michael E.; Fortune, Torben; Kaplar, Robert J.

An AlN barrier high electron mobility transistor (HEMT) based on the AlN/Al0.85Ga0.15N heterostructure was grown, fabricated, and electrically characterized, thereby extending the range of Al composition and bandgap for AlGaN channel HEMTs. An etch and regrowth procedure was implemented for source and drain contact formation. A breakdown voltage of 810 V was achieved without a gate insulator or field plate. Excellent gate leakage characteristics enabled a high Ion/Ioff current ratio greater than 107 and an excellent subthreshold slope of 75 mV/decade. A large Schottky barrier height of 1.74 eV contributed to these results. In conclusion, the room temperature voltage-dependent 3-terminal off-state drain current was adequately modeled with Frenkel-Poole emission.

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TYPE Journal Article YEAR 2016
DOIOSTI

Al00.3Ga0.7N PN diode with breakdown voltage >1600 V

Electronics Letters

Allerman, Andrew A.; Armstrong, Andrew A.; Fischer, Arthur J.; Dickerson, Jeramy; Crawford, Mary H.; King, Michael P.; Moseley, Michael W.; Wierer, J.J.; Kaplar, Robert J.

Demonstration of Al00.3Ga0.7N PN diodes grown with breakdown voltages in excess of 1600 V is reported. The total epilayer thickness is 9.1 μm and was grown by metal-organic vapour-phase epitaxy on 1.3-mm-thick sapphire in order to achieve crack-free structures. A junction termination edge structure was employed to control the lateral electric fields. A current density of 3.5 kA/cm2 was achieved under DC forward bias and a reverse leakage current <3 nA was measured for voltages <1200 V. The differential on-resistance of 16 mΩ cm2 is limited by the lateral conductivity of the n-type contact layer required by the front-surface contact geometry of the device. An effective critical electric field of 5.9 MV/cm was determined from the epilayer properties and the reverse current–voltage characteristics. To our knowledge, this is the first aluminium gallium nitride (AlGaN)-based PN diode exhibiting a breakdown voltage in excess of 1 kV. Finally, we note that a Baliga figure of merit (Vbr2/Rspec,on) of 150 MW/cm2 found is the highest reported for an AlGaN PN diode and illustrates the potential of larger-bandgap AlGaN alloys for high-voltage devices.

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TYPE Journal Article YEAR 2016
DOIOSTI
Results 201–225 of 346
Results 201–225 of 346
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