Research Updates

September 2019

Non-destructive characterization of thin layer resonant tunneling diodes

We present an advanced nondestructive characterization scheme for high current density AlAs/InGaAs resonant tunneling diodes pseudomorphically grown on InP substrates. We show how low-temperature photoluminescence spectroscopy (LT-PL) and high-resolution X-ray diffractometry (HR-XRD) are complementary techniques to increase the confidence of the characterized structure. The lattice-matched InGaAs is characterized and found to be of high quality. We discuss the inclusion of an undoped “copy” well (C-well) in terms of enhancements to HRXRD and LT-PL characterization and quantify the improved precision in determining the structure. As a consequence of this enhanced precision in the determination of physical structure, the AlAs barriers and quantum well (QW) system are found to contain nonideal material interfaces. Their roughness is characterized in terms of the full width to half-maximum of the split LT-PL emission peaks, revealing a ±1 atomic sheet variance to the QW width. We show how barrier asymmetry can be detected through fitting of both optical spectra and HR-XRD rocking curves.

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