Calculated threshold voltage adjusted to experimental data (line, Φ B = 0.86 eV) based on equations (3) in Ref. 3 as a function of the Al content in the barrier layer. Experimental data of process control monitor transistors (average of 21 sites per wafer) are given by squares. The values for x >12% are from Ref. 3.
Sheet carrier concentration of undoped AlxGa1−xN/GaN HEMT structures determined by Hall effect measurements of as-grown samples (full squares) and with a Ni Schottky contact (open squares) as well as by CV profiling using a GaN/mercury Schottky contact (open circles) on s.i. SiC substrates as a function of the Al content in the barrier layer. The lines are calculated based on Eq. (1) with n 0 = 0.01 (full line) for the Hall effect data of the as-grown samples and 0.155 (dotted line) for the CV profiling data. The bold line is determined from Φ B = 0.86 eV with n 0 = 0.139 (Ref. 3). In the inset, μH of the appropriate results is shown versus Al content on as-grown samples (full squares) and with a Ni Schottky contact (open squares). The lines are linear fits, only intended as a guide to the eye.
Surface potential of undoped AlxGa1−xN/GaN HEMT structures as determined from Hall effect data of as-grown samples (full squares), with a Ni Schottky contact (open squares), and CV profiling data (open circles) by means of the parameter n 0 in (1) as a function of the Al content in the barrier layer (Ref.3). The standard deviation of the results of Hall effect on as-grown samples and CV profiling is indicated by shaded areas. Photoreflectance data of selected samples are included (diagonal crosses). The full (as-grown samples, (0.26 ± 0.04) eV) and dashed (CV profiling, (0.94 ± 0.09) eV) lines of Φ B are the respective average values determined from the parameter n 0 in Eq. (1). The bold line Φ B = 0.86 eV is determined from Uth . The dashed line is a linear fit to the Φ B values determined from Hall effect data for x < 13%, intended as a guide to the eye.
Results of the evaluation of the Hall effect data using a two-layer model together with the results of the Hall effect measurements (squares) versus Al content. Shown are the total number of electrons ns (full line), 2DEG carriers n2D (dash-dotted line), and the carriers nr in the AlxGa1−xN (dashed line). In the inset, mobility data of the Hall effect measurements μH (squares) are shown together with the appropriate results of our calculation μ2D (dash-dotted line) and estimated μr (dashed line) versus Al content.
Measured mobility μH versus total carrier concentration ns . The full squares denote results of the as-grown samples. Below a value of ns = 4.5 × 1012 cm−2 we used Eq. (2) to determine ns . The open squares denote results obtained with Ni Schottky contacts.
Article metrics loading...
Full text loading...