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Optimum resonant tunnelling injection and influence of doping density on the performance of THz bound-to-continuum cascade lasers

2005; SPIE; Volume: 5727; Linguagem: Inglês

10.1117/12.590699

1996-756X

Jesse Alton, S. Barbieri, Chris Worral, Mark Houghton, Harvey E. Beere, Edmund Linfield, D. A. Ritchie,

Atmospheric Ozone and Climate

In this work we have investigated the operation of a recently demonstrated bound-to-continuum quantum cascade laser emitting at 2.9 THz under different active region doping densities. In addition, we have studied the injection efficiency as a function of the thickness of the Al0.15Ga0.85As barrier controlling the tunnel coupling between the superlattice miniband and the upper state of the laser transition. By tuning these two parameters threshold current densities as low as 52 A/cm2 and 83 A/cm2 were obtained at 5 K, corresponding to a reduction over the base design of 55% and 25% respectively. In both cases we attribute the improved threshold performance to a reduction of the parasitic leakage current. The decrease in threshold was always at the expense of a smaller laser dynamic operating range, which ultimately limited maximum operating temperatures in pulsed and continuous wave mode to 95 K and 80 K respectively.