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Proceedings ArticleDOI

GaN/AlGaN based complementary p + -p − -p-n + ATT-device for application in THz Imaging

01 Dec 2012-pp 1-4
Abstract: A detailed simulation investigation is carried out on the hetero-structure complimentary (p+-p−-p-n+) IMPATT oscillator for Terahertz power generation It is observed that this newly proposed GaN/AlGaN IMPATT may generate a pulsed power density of ∼8×1010 Wm−2 with an efficiency of 11%, whereas it's flatly doped counterpart is capable of delivering a pulsed power density of only 3×1010 Wm−2 with 7% efficiency The total parasitic series resistance, R S , including that due to the un-depleted region in device and also the effects of ohmic contact resistances, has been found to be a major problem that reduces the negative resistance significantly and thus it has a detrimental effect on THz oscillation of the device The study reveals that the value of R S decreases by 40% as the structure, semiconductor material pair as well as doping profile of the diode changes suitably from conventional to the proposed hetero-structure p+-p−-p-n+ type, by incorporating a 300A0 Al 04 Ga 06 N layer in the p-drift region This first study will be a useful guide in the THz-sector to meet the ever-increasing demand of semiconductor THz-sources for application in Imaging or in improvised explosive device (IED) detection
Topics: Ohmic contact (52%), Diode (51%), Negative resistance (51%), Equivalent series resistance (51%)
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Journal ArticleDOI
Abstract: We report optical rectification and subsequent generation of subpicosecond submillimeter‐wave radiation from a nonlinear organic crystalline salt. With optical excitation at a wavelength of 820 nm and a 150 fs pulse duration, the magnitude of the rectified field from the organic salt dimethyl amino 4‐N‐methylstilbazolium tosylate is one and two orders of magnitude larger than that from GaAs and LiTaO3 crystals, respectively. This organic crystal presently provides the most intense terahertz radiated field among all of the natural nonexternally biased materials we know.

233 citations

Journal ArticleDOI
Abstract: A new method is given for determining the electrical series resistance of an IMPATT diode. The measurement is based on observation of the oscillation threshold bias current for a diode in a standard circuit. The method is applied to GaAs diodes near 40 GHz. The values obtained are used to quantitatively explain other performance characteristics of the diodes.

53 citations

Journal ArticleDOI
Abstract: Reliability of terahertz-frequency (~1.0 THz) characteristics of wide-bandgap (WBG) wurtzite (Wz)-GaN- and 4H-SiC-based p++nn++-type single-drift-region (SDR) impact avalanche transit time (IMPATT) devices (normal and photoilluminated) is compared through a simulation scheme. The simulation experiment reveals that an RF power density of 3.37 times 1011 W middotm-2 (efficiency of 18.2%) at around 1.126 THz may be realized from the optimized unilluminated GaN IMPATT device, whereas the unilluminated 4H-SiC IMPATT device is expected to generate an RF power density of 1.35 times 1011 W middotm-2 (efficiency of 9%) at 1.05 THz. However, the parasitic series resistance reduces the maximum exploitable power density from the terahertz devices. Under optical illumination, additional photogenerated carriers are created in the devices, and these carriers change the admittance and negative resistance properties of the terahertz IMPATT diodes. The performance modulation of the terahertz devices is simulated, and the results are compared in this paper. Under external radiation, the operating frequencies of the GaN- and SiC-based diodes are found to shift upward by 6.0 and 40.0 GHz, respectively, with degradation of maximum output-power density level and device negative resistance. The extensive simulation experiments establish that, although the photosensitivity of the 4H-SiC-based IMPATT device is better than its GaN counterpart, the overall terahertz performance of the unilluminated GaN IMPATT device is far better than the 4H-SiC-based device, particularly in terms of output power and efficiency. The simulation results and the proposed experimental methodology presented here can be used for realizing optically tuned WBG IMPATT oscillators for terahertz communication.

51 citations

"GaN/AlGaN based complementary p + -..." refers background in this paper

  • ...GaN is less noisy and is chemically very stable at high temperature [1]....