Physics, growth, and performance of (In,Ga)As–AlP/InP quantum‐cascade lasers emitting atλ< 4 μm

The design strategy and performance for short wavelength (λ⪅ 4 μm) quantum‐cascade lasers (QCLs) is discussed. The QCLs are based on strain‐compensated AlAs–In0.73Ga0.27As heterostructures grown using gas‐source molecular‐beam epitaxy on InP substrates. Both composite barriers based on AlAs–In0.55Al0.45As and composite wells based on In0.73Ga0.27As–In0.55Al0.45As are used to achieve laser emission at wavelengths as short as 3.05 µm by avoiding leakage from the upper laser state into either the higher‐lying miniband or into indirect states within the heterostructure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)