Carrier Density and Inter Valence Band Absorption in InGaAs(P) Lasers

A method is presented that allows the determination of the carrier density in semiconductor lasers above and below threshold. This method is based on a line shape analysis of the spontaneous emission. Corresponding gain values can be calculated from the carrier density. Temperature dependent measurements of the spontaneous emission and the differential quantum efficiency allow the determination of the optical losses at laser threshold. The result is a strong influence of inter valence band absorption on the threshold of 1.65 μm InGaAs lasers and an extremely weak influence on 1.3μm InGaAsP lasers.