Full two-dimensional electroluminescent analysis of GaAs/AlGaAs HBTs

Full two-dimensional electroluminescent techniques have been developed and applied to HBTs for the first time to reveal the growth and progression of dark-line defects in AlGaAs HBTs at elevated current densities. Bias studies have shown that at high current densities, HBT base-emitter junctions degrade resulting in regions that exhibit non-radiative recombination. Defects in the epitaxial material can lead to current driven dislocation propagation caused by recombination enhanced dislocation climb and recombination enhanced dislocation glide. At current densities on the order of 100 KA/cm², formation of dark-line defects occurs within 92 hours. At current densities approaching 150 KA/cm², rapid changes (within hours) are observed in the EL pattern; however, little change in the dc and RF characteristics are seen in the short term. This demonstrates that the EL technique is a sensitive indicator of material changes in devices well before any electrical manifestation