24
S. J. Mukhopadhyay et al.
THz frequency band has enormous necessity like imaging [7], spectrum analysis
[8], nano-electronic [9], inspection services [10, 11], drug industry [12, 13], space
research [14], etc. Despite enormous application probability of THz frequency band,
this area is yet to be utilized because of unavailability of potential solid-state sources
that may produce, identify terahertz frequencies. In the last part of the twentieth century, when the development of IMPATT devices gained its momentum then basically
fabrication was done by using germanium (Ge) and silicon (Si) as semiconducting substance. But at present, Ge IMPATTs are no longer in existence. Due to very
fast development of Si process technology, single-drift and double-drift region (i.e.,
SDR and DDR) Si IMPATTs have received appreciable attention due to capacity of
producing greater RF power with considerable conversion efficiency at mm-wave
frequencies [15–18].
Recently, wide bandgap (WBG) materials like SiC and diamond IMPATT sources
exhibited the capacity of producing high mm-wave and terahertz power [19–22]. The
group IV-IV compound material SiC has different polytypes forms like 2H-SiC, 4HSiC, 6H-SiC, and 3C-SiC; fabrication of 4H-SiC IMPATT source has already been
reported [21]. However, very low RF power output (in the order of milli-watts) was
reported from 4H-SiC IMPATT source at microwave frequencies [21]. Simulations
reveal that the 4H-SiC IMPATTs possess the capacity of generating high mm-wave
power (~watts) with significantly high efficiency [19, 20, 22]. One major problem
of 4H-SiC IMPATT devices is its high series resistance. This high series resistance
problem can be eliminated by replacing 4H-SiC with 3C-SiC since the mobility of
electrons and holes in 3C-SiC are higher than those of 4H-SiC. Thus, authors have
taken 3C-SiC-based IMPATTs for operation at high-frequency regime.
Type-IIb diamond being very inspiring WBG material and researchers have preferred it for best quality features. In the year 1976, it was termed as carbon and
afterward it was synthesized in 1954. The favorable mechanical and thermal properties of diamond coupled with the development of its growth technique made great
interest to utilize this substance to fabricate high-power-high-frequency semiconductor devices. Devices which are diamond-based like MESFET, IMPATT diode,
and BJT have been reported by Trew et al. in 1991 as useful sources of microwave
power [23]. Diamond-based IMPATTs can also be developed as potential high-power
mm-wave [24] and THz sources.
As far as this chapter is concerned, the results of a co-relative research among
Si, 3C-SiC, and type-IIb diamond-based IMPATT sources operating at various mmwaves, and THz frequency bands have been presented. This comparative study is very
much important in order to discover the potency of 3C-SiC IMPATT as a suitable
solid-state source at the specified frequency bands.
S. J. Mukhopadhyay et al.
THz frequency band has enormous necessity like imaging [7], spectrum analysis
[8], nano-electronic [9], inspection services [10, 11], drug industry [12, 13], space
research [14], etc. Despite enormous application probability of THz frequency band,
this area is yet to be utilized because of unavailability of potential solid-state sources
that may produce, identify terahertz frequencies. In the last part of the twentieth century, when the development of IMPATT devices gained its momentum then basically
fabrication was done by using germanium (Ge) and silicon (Si) as semiconducting substance. But at present, Ge IMPATTs are no longer in existence. Due to very
fast development of Si process technology, single-drift and double-drift region (i.e.,
SDR and DDR) Si IMPATTs have received appreciable attention due to capacity of
producing greater RF power with considerable conversion efficiency at mm-wave
frequencies [15–18].
Recently, wide bandgap (WBG) materials like SiC and diamond IMPATT sources
exhibited the capacity of producing high mm-wave and terahertz power [19–22]. The
group IV-IV compound material SiC has different polytypes forms like 2H-SiC, 4HSiC, 6H-SiC, and 3C-SiC; fabrication of 4H-SiC IMPATT source has already been
reported [21]. However, very low RF power output (in the order of milli-watts) was
reported from 4H-SiC IMPATT source at microwave frequencies [21]. Simulations
reveal that the 4H-SiC IMPATTs possess the capacity of generating high mm-wave
power (~watts) with significantly high efficiency [19, 20, 22]. One major problem
of 4H-SiC IMPATT devices is its high series resistance. This high series resistance
problem can be eliminated by replacing 4H-SiC with 3C-SiC since the mobility of
electrons and holes in 3C-SiC are higher than those of 4H-SiC. Thus, authors have
taken 3C-SiC-based IMPATTs for operation at high-frequency regime.
Type-IIb diamond being very inspiring WBG material and researchers have preferred it for best quality features. In the year 1976, it was termed as carbon and
afterward it was synthesized in 1954. The favorable mechanical and thermal properties of diamond coupled with the development of its growth technique made great
interest to utilize this substance to fabricate high-power-high-frequency semiconductor devices. Devices which are diamond-based like MESFET, IMPATT diode,
and BJT have been reported by Trew et al. in 1991 as useful sources of microwave
power [23]. Diamond-based IMPATTs can also be developed as potential high-power
mm-wave [24] and THz sources.
As far as this chapter is concerned, the results of a co-relative research among
Si, 3C-SiC, and type-IIb diamond-based IMPATT sources operating at various mmwaves, and THz frequency bands have been presented. This comparative study is very
much important in order to discover the potency of 3C-SiC IMPATT as a suitable
solid-state source at the specified frequency bands.