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Electron mobility in very low density GaN/AlGaN/GaN heterostructures

Electron mobility in very low density GaN/AlGaN/GaN heterostructures. M. J. Manfra,a) K. W. Baldwin, and A. M. Sergent Bell Laboratories, Lucent Technologies, 700 Mountain Avenue, Murray Hill, New Jersey 07974 R. J. Molnar and J. Caissie

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Electron mobility in very low density GaN/AlGaN/GaN heterostructures

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  1. Electron mobility in very low density GaN/AlGaN/GaN heterostructures M. J. Manfra,a) K. W. Baldwin, and A. M. Sergent Bell Laboratories, Lucent Technologies, 700 Mountain Avenue, Murray Hill, New Jersey 07974 R. J. Molnar and J. Caissie Massachusetts Institute of Technology, Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420-9108

  2. Sample • MBE-1.5μm GaN 16nm Al0.06Ga0.94N 3 nm GaN • Mesa-100 nm • Ohmic contact -Ti/Al/Ni/Au annealed at 800。C 30Sec • Hall bar:wide-100μm long-2 mm • SiO2-100nm • Gate-( Ni 10 nm/Au 100 nm )

  3. (a) Measured 2DEG density at T=0.3 K as a function of gate voltageVgbetween 1 and −4.25 V. In this regime, nsvs Vgis linear and well approximated by ne=1.23x1012+2.42x1011 cm−2 *Vg. • (b) 2DEG sheet resistance as a function of electron density at T=0.3 K.

  4. (Color) Mobility at T=0.3 K solid black curve is the experimentally measured mobility as a function of 2DEG density from ,2x1011 to , 2x1012 cm−2. For comparison, the red line displays the function μ1~ne1.0 at low density and the blue line represents μ2~ne−1.5 in the high-density regime. The open black squares are calculated from μT=1/(μ1−1+ μ2−1).

  5. Integer quantum Hall states (Rxx~0) • As the gate voltage is changed from −1 to −3 V the 2DEG density is reduced from 9.8x1011 to 5x1011 cm−2. • the integer quantum Hall state near 10 T (Rxx=0) can be progressively shifted from n=4, to n=3, and to n=2

  6. Summary • Grown high mobility and low density AlGaN/GaN hetero-structure • At low electron density the mobility obeys a power-law dependence ( μ~ne1.0)

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