TEMPERATURE-DEPENDENCE OF THE THRESHOLD CURRENT FOR INGAALP VISIBLE LASER-DIODES

The temperature dependence of the threshold current for InGaAIP visible light laser diodes was investigated from the aspect of gain-current characteristics. The cavity length dependence of light output power versus current characteristic was evaluated for a 40-mu-m width InGaP-InGaAIP broad-stripe laser in the temperature range between -70 and 90-degrees-C, which had about a 670 nm oscillation wavelength at room temperature. The threshold-current density dependence on the cavity length shows that a linear-gain approximation is suitable for this system. A minimum threshold-current density of 860 A/cm2 was achieved at room temperature with a cavity length of 1160-mu-m, which is the lowest value ever reported for this material. The linear-gain parameters beta and J0 depended on the temperature with the characteristic temperature of about 200 K, which is considered to be the intrinsic characteristic temperature of the threshold current for this active-layer material. The internal quantum efficiency, derived from the cavity length dependence of the differential quantum efficiency, decreased in the temperature range higher than -10-degrees-C, which affected the excess threshold-current increase and the decrease in the characteristic temperature at this temperature range. The theoretical calculation, considering a one-dimensional band structure model, showed that this excess increase of the threshold current was found to be attributed to the electron overflow current into the p-type cladding layer.