We propose an array of unbiased antennaless continuous wave (CW) THz photomixers made of subwavelength buried metal–semiconductor–metal (MSM) gratings with dissimilar Schottky barriers. These dissimilar metals in each unit cell are in intimate contact, and yet the maximum electric field appearing in the semiconducting material, unlike that in the planar structures, is far below its breakdown threshold. This relaxes the breakdown constraint that is normally confronted in the design of similar THz emitters with planar gratings. Besides, as compared with a similar array with subwavelength but planar MSM gratings, use of the buried MSM has increased the volume in which the carriers’ photogeneration occurs, enhancing the resultant CW THz radiation by an order of magnitude. This is also five orders of magnitude greater than the THz power that can be radiated by a similar array of the same size with diffraction-limited planar electrodes. Moreover, calculating the frequency dependence of the THz output power, the newly proposed plasmons-assisted emitters are shown to be tunable in a wide range of 0.1–3 THz. We have also numerically demonstrated that 4.5% of the 1.58 mW optical pump can efficiently be converted to the THz power at the radiation frequency of 0.5 THz
