Tall-barrier terahertz quantum cascade lasers

A terahertz quantum cascade laser is presented in which selectively placed pure AlAs barriers are used to reduce parasitic leakage currents to the conduction band continuum. The design is demonstrated to have improved temperature performance over a regrowth of the current T-max similar to 200K record holder (181 K vs. 175 K). Strangely, it fails to lase below similar to 70 K, which we attribute to negative differential resistance (NDR) prior to threshold. A subsequent design using only AlAs barriers failed to lase, the reason for which we posit to be either early NDR or excessive interface roughness scattering. (C) 2013 AIP Publishing LLC.