GaN-Based Gunn Diodes: Their Frequency and Power Performance and Experimental Considerations

Egor ALEKSEEV  Dimitris PAVLIDIS  William Earl SUTTON  Edwin PINER  Joan REDWING  

IEICE TRANSACTIONS on Electronics   Vol.E84-C   No.10   pp.1462-1469
Publication Date: 2001/10/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Joint Special Issue on Heterostructure Microelectronics with TWHM 2000 (Topical Workshop on Heterostructure Microelectronics 2000))
Category: Novel Electron Devices
GaN,  THz,  Gunn,  NDR,  

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Theoretical and experimental aspects of GaN-based Gunn diodes are reviewed. Since the threshold field for Gunn effect in GaN (FTH>150 kV/cm) is reported to be much higher than in GaAs (FTH=3.5 kV/cm), the active layer of GaN-based devices can be made thinner (<3 µm) and doped higher (>1017 cm-3) than in conventional Gunn diodes. Consequently, GaN-based devices are expected to offer increased frequency and power capabilities. The advantages of GaN are demonstrated with the help of large-signal simulations of GaN and GaAs Gunn diodes. The simulations revealed that GaN diodes can be operated at a higher frequency (up to 760 GHz vs. 100 GHz) and with larger output power density (105 W/cm2 vs. 103 W/cm2) than GaAs diodes. Epitaxial layers of n+/n-/n+ GaN (1019 cm-3/1017 cm-3/1019 cm-3) designed for millimeter-wave operation were grown using MOCVD on SiC substrates. GaN Gunn diodes with 4 µm-thick active layers were fabricated using specially developed dry etching techniques. The RIE was optimized to allow deep low-damage etching and allowed reduction of contact resistivity of etched layers (RC10-6 Ωcm2). GaN diodes fabricated on SiC substrates with high thermal conductivity were tested on-wafer and demonstrated high voltage and current capability (60 V and 2.5 A). High frequency testing of these devices requires proper dicing, mounting on efficient heatsinks, and connection to appropriate oscillator cavities.