The observation of terahertz (THz) intersubband emission from GaAs/AlGaAs quantum cascade structures employing higher energy interface and barrier confined AlAs-like phonons for depopulation is reported. Emission is observed at 12.0 meV (2.9 THz) and 17.5 meV (4.2 THz) with full-width at half-maximum of 0.7 and 1.6 meV, respectively, at T=10 K from two different structures. The structures consisted of 40 periods of the quantum cascade module and relied on spatially diagonal (interwell) transition for the terahertz emission. The possibility of tuning the emission frequency using quantum confined Stark effect is also demonstrated. [Copyright &y& Elsevier]