Reliability characterization of MOVPE grown n-GaInP/p-GaAs heterojunctions vis-a-vis high temperature operation through photoreflectance spectroscopy, transmission electron microscopy and deep level transient spectroscopy

Abstract

The paper presents a detailed characterization of the lattice-matched n-GaInP/p-GaAs heterostructures, including the evolution of the heterojunction and its departure from the initial state under elevated temperatures and current stress. GaInP/GaAs heterojunctions, which constitute the emitter-base junction for contemporary HBTs, were generated using MOVPE. Photoreflectance spectroscopy (PR) has been used to determine the GaInP ordering and bandgap energy, while cross-section TEM has been used to determine the GaInP/GaAs interface region for evidence of defects. p-n tunnel diode samples were generated and characterized to determine the rate of carbon diffusivity under temperature and current induced effects, to provide quantitative measurement of degradation of HBT base layer as seen from carbon precipitate-type artifacts from XTEM analysis. Moreover, n-GaInP/p/sup +/-GaAs diodes were generated for deep-level transient spectroscopy (DLTS) to gain information on traps and trap kinetics from current-stress. The data from the various characterization techniques is utilized to provide the degradation mechanisms for n-GaInP/p-GaAs HBTs. While no evidence of dislocations at the GaInP/GaAs interface was found in our samples, a model for determination of the relaxation time for dislocation scattering is also presented.