MICROAMPERE THRESHOLD CURRENT OPERATION OF GAAS AND STRAINED INGAAS QUANTUM-WELL LASERS AT LOW-TEMPERATURES (5-K)

The operation of ultralow threshold current GaAs and InGaAs quantum well lasers at cryogenic temperatures has been studied. In particular the threshold current I(th) and lasing wavelength of GaAs and strained InGaAs lasers have been measured as a function of temperature from 300 down to 5 K. I(th) can in both lasers be characterized by a linear function of temperature up to 200 K, with a significantly (2.5 X) larger dI(th)/dT for the GaAs laser. We measured a minimum threshold current of 120-mu-A for the GaAs laser and 165-mu-A for the InGaAs laser at 5 K. We derive a simple expression for the transparency carrier density as a function of temperature and effective masses to explain our results.