Microampere threshold current operation of GaAs and strained InGaAs quantum well lasers at low temperatures (5 K)

Abstract

The operation of ultralow threshold current GaAs and InGaAs quantum well lasers at cryogenic temperatures has been studied. In particular the threshold current Ith and lasing wavelength of GaAs and strained InGaAs lasers have been measured as a function of temperature from 300 down to 5 K. Ith can in both lasers be characterized by a linear function of temperature up to 200 K, with a significantly (2.5×) larger dIth/dT for the GaAs laser. We measured a minimum threshold current of 120 μA for the GaAs laser and 165 μA 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.

Low Temperature Behaviour of Laser Diodes

“…This may involve with the device capacitance some parasitic low frequency cut-off that limits seriously the bandwidth [5]. The resonant frequency is an important laser parameter.…”

Sub-100 μA current operation of strained InGaAs quantum well lasers at low temperatures

“…The lowest threshold current demonstrated is smaller by about a factor of 3 than the best previous results. 3 The laser diodes used in the study are graded index separate confinement heterostructure ͑GRINSCH͒ strained InGaAs/AlGaAs single quantum well ͑SQW͒ lasers. The GRINSCH strained InGaAs/AlGaAs SQW wafer was grown on ͑100͒ n-GaAs substrate by molecular beam epitaxy ͑MBE͒.…”

“…Note that this difference in InGaAs QW lasers is much larger than that in GaAs QW lasers. 3 The reason is that the InGaAs QW has a deeper QW and the injected holes in InGaAs QW have a smaller effective mass due to the strain effect. In summary, we have quantified the decrease of threshold current and the saturation in external quantum efficiency with decreasing temperatures in strained InGaAs SQW BH lasers.…”