Direct Au–Au bonding technology for high performance GaAs/AlGaAs quantum cascade lasers

Abstract

In this paper we investigate chip bonding technology of GaAs/AlGaAs quantum cascade lasers (QCLs). Its results have strong influence on final performance of devices and are essential for achieving room temperature operation. Various solders were investigated and compared in terms of their thermal resistance and induced stress. The spatially resolved photoluminescence technique has been applied for a device thermal analysis. The soldering quality was also investigated by means of a scanning acoustic microscopy. The particular attention has been paid to Au–Au die bonding, which seems to be a promising alternative to the choice between hard and soft solder bonding of GaAs/AlGaAs QCLs operating from cryogenic temperatures up to room temperatures. A good quality direct Au–Au bonding was achieved for bonding parameters comparable with the ones typical for AuSn eutectic bonding process. High performance room temperature operation of GaAs/AlGaAs QCLs has been achieved with the state-of-the-art parameters.