Diamond wafer -based plasmonic terahertz devices

Terahertz field-effect transistors (TeraFETs) based on plasma waves have been developed in a variety of material systems including silicon , InGaAs, and graphene and demonstrated their potential for terahertz detection, generation imaging , and wireless communication . Pdiamond has lately been presented as a potential material for plasma wave THz technologies. A prospective material for high-power and high-temperature applications, diamond has a broad bandgap (bandgap 5.46 eV), strong dielectric strength (between 5 and 10 MV/cm), and high thermal conductivity (23 W/cmK) . Moreover, as a result of diamond's large optical phonon energy (~165 meV), optical phonon scattering is suppressed to as much as 400 K. A long diamond momentum relaxation time makes it easier to satisfy the criterion for generating plasmonic resonance ωpτ > 1, where plasma frequency is denoted by ωp. Diamond is therefore a viable material for detecting THz signals from 240 GHz to 600 GHz openings, which may be assigned for much further than-5Gwireless networks using resonance response. Diamond TeraFETs also have low ohmic contact resistance, making them even more appealing for THz applications [9]. In contrast to pdiamond, n-diamond has a lower effective mass (meff=0.36m0) but it has a higher maximum carrier mobility of 7300 cm2/Vs at 300K (compared to 5,300 cm2/Vs for p-diamond that has been utilized so far to realize FETs . 

Hydrodynamic simulations of the diamond transport properties link the maximum operating frequency of a TeraFET to the minimum FET response time (see Fig. 1). Diamond FET performance and THz detection and emission analysis have been reported in [9, 12]. We are going to discuss some of these results in this section. As mentioned in the introduction section, among all of the excellent properties of the diamond the most important one is the high momentum relaxation time and the quality factor, Q = ωpτ. The value of ωpτ needs to be over 1 to get a resonant detection. As was reported in [9], p-diamond can get a resonant detection even for a fairly low sub-THz frequency (~300 GHz), see Fig. 1 showing the momentum relaxation time and quality factor at 300 GHz for different mobilities. Table 1 lists the parameters used for Fig. 1. 

To summarize, p-diamond have the lowest critical resonant mobility thus a strong contender for resonant detections uses. It has wide range of frequency tenability even in the sub-THz regime with larger resonant peaks making it useful for 5G/6G THz communications as well. We have studied the n-diamond frequency response with respect to channel length and temperature for furture THz applications. We have illustrated the effects of the viscosity as well. Finally, both p- and ndiamond demonstrated high THz resonance response atcryogenic, room and elevated temperatures. 

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