Enhanced Mobility in InAlN/AlN/GaN HEMTs Using a GaN Interlayer

• Published in: IEEE transactions on electron devices Vol. 66; no. 7; pp. 2910 - 2915
• Main Authors: Malmros, Anna, Chen, Jr-Tai, Hjelmgren, Hans, Lu, Jun, Hultman, Lars, Kordina, Olof, Sveinbjornsson, Einar O., Zirath, Herbert, Rorsman, Niklas
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-07-2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aluminum gallium nitride; Aluminum nitride; Cryoforming; Cryogenic effects; Cryogenic temperature; Electron mobility; Gallium nitride; Gallium nitrides; GaN; HEMT; HEMTs; Heterostructures; High electron mobility transistors; InAlN; interlayer (IL); Interlayers; mobility; MODFETs; Quantum wells; Scattering; Semiconductor devices; Temperature measurement; Variations; Wide band gap semiconductors; InAlN; mobility; GaN; HEMT; Cryogenic temperature; interlayer (IL)
• ISSN: 0018-9383; 1557-9646; 1557-9646
• DOI: 10.1109/TED.2019.2914674

An enhancement of the electron mobility (<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>) in InAlN/AlN/GaN heterostructures is demonstrated by the incorporation of a thin GaN interlayer (IL) between the InAlN and AlN. The introduction of a GaN IL increases <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula> at room temperature (RT) from 1600 to 1930 cm 2 /Vs. The effect is further enhanced at cryogenic temperature (5 K), where the GaN IL sample exhibits a <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula> of 16000 cm 2 /Vs, compared to 6900 cm 2 /Vs without IL. The results indicate the reduction of one or more scattering mechanisms normally present in InAlN/AlN/GaN heterostructures. We propose that the improvement in <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula> is either due to the suppression of fluctuations in the quantum well subband energies or to reduced Coulomb scattering, both related to compositional variations in the InAlN. HEMTs fabricated on the GaN IL sample demonstrate larger improvement in dc- and high-frequency performance at 5 K; <inline-formula> <tex-math notation="LaTeX">{f}_{\text {max}} </tex-math></inline-formula> increases by 25 GHz to 153 GHz, compared to an increase of 6 GHz to 133 GHz without IL. The difference in improvement was associated mainly with the drop in the access resistances.