Abstract: A high electron mobility transistor (HEMT) including a channel; a barrier confining mobile charge carriers in the channel; a drain contact to the channel; a source contact to the channel; and a gate contact coupled to the channel and modulating a current, comprising the mobile charge carriers flowing in response to a voltage VSD applied between the source contact and the drain contact, when an RF signal electric field and DC bias electric field are applied between the gate contact and the source contact. An offset between the conduction bands of the channel and barrier is increased to a level that suppresses real space transfer noise associated with a portion of the mobile charge carriers being thermionically emitted out of the channel into the barrier when the VSD is applied, wherein the RST noise is reduced by at least a factor of two as compared to a HEMT where the alloy composition of the barrier is lattice matched.

Abstract: A solar thermal absorber including a spectrally selective filter comprising a stack of dielectric layers and one or more semiconductor absorber layers. The dielectric layers are transparent to infrared radiation and have a refractive index contrast, and the semiconductor absorber layers have a band gap, such that the semiconductor absorber layers absorb at least a portion of the solar spectrum and the stack reflects infrared radiation.

Abstract: A solar thermal absorber including a spectrally selective filter comprising a stack of dielectric layers and one or more semiconductor absorber layers. The dielectric layers are transparent to infrared radiation and have a refractive index contrast, and the semiconductor absorber layers have a band gap, such that the semiconductor absorber layers absorb at least a portion of the solar spectrum and the stack reflects infrared radiation.