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. SergentBell Laboratories, Lucent Technologies, 700 Mountain Avenue, Mu

rray Hill, New Jersey 07974R. J. Molnar and J. Caissie

Massachusetts Institute of Technology, Lincoln Laboratory, 244 Wood Street, Lexington,

Massachusetts 02420-9108

SampleSample

MBE-1.5μm GaNMBE-1.5μm GaN 16nm Al16nm Al0.060.06GaGa0.940.94NN 3 nm GaN3 nm GaN Mesa-100 nmMesa-100 nm Ohmic contact -Ti/Al/Ni/AuOhmic contact -Ti/Al/Ni/Au annealed at 800annealed at 800 。。 C 30SecC 30Sec Hall bar:wide-100μmHall bar:wide-100μm long-2 mmlong-2 mm SiOSiO22-100nm-100nm Gate-( Ni 10 nm/Au 100 nm )Gate-( Ni 10 nm/Au 100 nm )

(a) Measured 2DEG density at T=0.3 K as a function of gate voltageVg between 1 and −4.25 V. In this regime, ns vs Vg is 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.

(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).

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

SummarySummary

Grown high mobility and low density Grown high mobility and low density AlGaN/GaN hetero-structureAlGaN/GaN hetero-structure

At low electron density the mobility At low electron density the mobility obeys a power-law dependence obeys a power-law dependence ( μ~n( μ~nee

1.01.0))