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R. Singh et al.
access resistance, and capless annealing process [39]. AlGaN/GaN HEMT with nonalloyed ion implanted ohmic contacts [40] showed PAE of 72% and power density of
6.8 W/mm at 4 GHz. More recently, InAlN/GaN HMET fabricated with non-alloyed
regrown n+-GaN ohmic contacts demonstrated f MAX of 405 GHz for PA applications
in G-band (140–220 GHz) [41].
A comparison of different semiconductor device technologies based on
continuous-wave (CW) output power versus operating frequency is shown in Fig. 3a,
which shows GaN power amplifiers output power decreases with increase in frequency by 1/f up to 30 GHz, 1/f
2 between 30 and 100 GHz, and 1/f
3 beyond 100 GHz
due to maximum operational drain voltage and total gate periphery. Although using
different FP arrangements, higher P OUT was achieved. Most RF applications with
high P OUT and high PAE are critically important to reduce power consumption
and heat dissipation in a significant manner, that led less requirements of cooling
arrangements which helps in reducing size and weight of the overall system [8].
Figure 3b depicts power output efficiency versus frequency from 2 to 94 GHz for
GaN HEMTs power amplifiers. It is noted that performance of power amplifiers in
terms of efficiency also affected below-frequency range <10 GHz due to the lower
cut-off frequency and limited gain [8].
As GaN materials have LO phonon of ~92 meV, power devices based on GaN
materials have shown good performance up to 10 THz frequencies (THz upper band)
at room temperature. Way back in ‘90s, pioneers Dyakonov and Shur [42] first proposed theoretical explanation of applications of FETs for THz spectroscopy by predicting plasma waves enabled variation in FET channel current. Subsequent years
witnessed, FET as an efficient broadband THz detector and their possible application for THz imaging [43–46], Si-MOSFET efficient room temperature detectors of
sub-THz radiation [47]. In a major technology breakthrough, Sun et al. [45] fabricated AlGaN/GaN HEMTs using optical lithography and detected terahertz radiation at room temperature via self-mixing, with a responsivity (3.6 kV/W). The
device having gate length of 2 μm and floating antennas isolated electrically from
Fig. 3 Comparison of GaN power amplifiers. a CW output power as a function of frequency,
b power added efficiency versus frequency
R. Singh et al.
access resistance, and capless annealing process [39]. AlGaN/GaN HEMT with nonalloyed ion implanted ohmic contacts [40] showed PAE of 72% and power density of
6.8 W/mm at 4 GHz. More recently, InAlN/GaN HMET fabricated with non-alloyed
regrown n+-GaN ohmic contacts demonstrated f MAX of 405 GHz for PA applications
in G-band (140–220 GHz) [41].
A comparison of different semiconductor device technologies based on
continuous-wave (CW) output power versus operating frequency is shown in Fig. 3a,
which shows GaN power amplifiers output power decreases with increase in frequency by 1/f up to 30 GHz, 1/f
2 between 30 and 100 GHz, and 1/f
3 beyond 100 GHz
due to maximum operational drain voltage and total gate periphery. Although using
different FP arrangements, higher P OUT was achieved. Most RF applications with
high P OUT and high PAE are critically important to reduce power consumption
and heat dissipation in a significant manner, that led less requirements of cooling
arrangements which helps in reducing size and weight of the overall system [8].
Figure 3b depicts power output efficiency versus frequency from 2 to 94 GHz for
GaN HEMTs power amplifiers. It is noted that performance of power amplifiers in
terms of efficiency also affected below-frequency range <10 GHz due to the lower
cut-off frequency and limited gain [8].
As GaN materials have LO phonon of ~92 meV, power devices based on GaN
materials have shown good performance up to 10 THz frequencies (THz upper band)
at room temperature. Way back in ‘90s, pioneers Dyakonov and Shur [42] first proposed theoretical explanation of applications of FETs for THz spectroscopy by predicting plasma waves enabled variation in FET channel current. Subsequent years
witnessed, FET as an efficient broadband THz detector and their possible application for THz imaging [43–46], Si-MOSFET efficient room temperature detectors of
sub-THz radiation [47]. In a major technology breakthrough, Sun et al. [45] fabricated AlGaN/GaN HEMTs using optical lithography and detected terahertz radiation at room temperature via self-mixing, with a responsivity (3.6 kV/W). The
device having gate length of 2 μm and floating antennas isolated electrically from
Fig. 3 Comparison of GaN power amplifiers. a CW output power as a function of frequency,
b power added efficiency versus frequency