Scanning tunneling microscopy (STM) studies of a semiconductor vertical-cavity surface-emitting laser (VCSEL) device viewed in cross section on an atomic scale are reported. The strained layer In0.2Ga0.8As/GaAs multiple-quantum wells (MQWs) in the laser active region are imaged with atomic resolution. For the first time, the interface roughness of In0.2Ga0.8As/GaAs MQWs is revealed by imaging spectroscopically different individual indium and gallium atoms. It was found that STM images can directly map the interface electronic structure of Al0.67Ga0.33As/GaAs multiple layers in the Bragg reflectors of the VCSEL. The images reflect enhanced or reduced interface electron concentration in region’s with a spatial extension of approximately 100 angstrom. The bias effect is also discussed in the imaging of heterostructures.