Heterojunction versus homojunction transit time devices atelevated junction temperature: performance comparison at MMwavewindow frequency
15 Oct 2012-Vol. 8549, pp 95-98
TL;DR: In this paper, the performance of Si/Si 0.8 Ge 0.2 heterojunction IMPATT devices is compared with those of homojunction devices in terms of negative resistance, device impedance and quality factor.
Abstract: Prospects of Si/Si 0.8 Ge 0.2 heterojunction IMPATT devices are studied through a modified simulation technique and their performances are further compared with those of homojunction devices. This high-frequency study includes the effects of mobile space charge, parasitic resistance and also considered the detrimental role of elevated junction temperature on the maximum exploitable power level from the devices. The study indicates that under similar operating condition, Si/SiGe heterojunction IMPATT is capable of delivering a RF-power output of nearly 6W (efficiency 21%), two times higher than that from Si 0.8 Ge 0.2 homojunction diode, which is only 13% efficient. The overall study indicates the superiority of the heterojunction diodes over their homojunction counterparts as far as negative resistance, device impedance and quality factor are concerned. To the best of author’s knowledge, this is the first report on highfrequency analysis of Si/Si 0.8 Ge 0.2 heterojunction IMPATT.
TL;DR: In this article, the performance of the GaN IMPATT diodes in the terahertz regime was investigated using a modified double iterative simulation technique and the effect of photo-illumination on the devices was investigated.
Abstract: The prospects of wurtzite phase single-drift-region (SDR), flat and single-low-high-low (SLHL) type GaN IMPATT devices as terahertz sources are studied through a simulation experiment. The study indicates that GaN IMPATT diodes are capable of generating high RF power (at least 2.5 W) at around 1.45 THz with high efficiency (17–20%). The superior electronic properties of GaN make this a promising candidate for IMPATT operation in the THz regime, unapproachable by conventional Si, GaAs and InP based IMPATT diodes. The effect of parasitic series resistance on the THz performance of the device is further simulated. It is interesting to note that the presence of a charge bump in a flatly doped SDR structure reduces the value of parasitic series resistance by 22%. The effects of photo- illumination on the devices are also investigated using a modified double iterative simulation technique. Under photo-illumination (i) the negative conductance and (ii) the negative resistance of the devices (both flat and SLHL) decrease, while the frequency of operation and the device quality factor shift upwards. However, the upward shift in operating frequency is found to be more (~16 GHz) in the case of the SLHL SDR IMPATT device. The study indicates that GaN IMPATT is a promising opto-sensitive high power THz source.
"Heterojunction versus homojunction ..." refers background or methods in this paper
TL;DR: In situ hydrogen cleaning to reduce the surface segregation of n-type dopants in SiGe epitaxy has been used to fabricate Si∕SiGe resonant tunneling diodes in a joint gas source chemical vapor deposition and molecular beam epitaxial system as mentioned in this paper.
Abstract: In situ hydrogen cleaning to reduce the surface segregation of n-type dopants in SiGe epitaxy has been used to fabricate Si∕SiGe resonant tunneling diodes in a joint gas source chemical vapor deposition and molecular beam epitaxial system. Diodes fabricated without the in situ clean demonstrate linear current-voltage characteristics, while a 15min hydrogen clean produces negative differential resistance with peak-to-valley current ratios up to 2.2 and peak current densities of 5.0A∕cm2 at 30K. Analysis of the valley current and the band structure of the devices suggest methods for increasing the operating temperature of Si∕SiGe resonant tunneling diodes as required for applications.