Microstructure of V-based ohmic contacts to AlGaN/GaN heterostructures at a reduced annealing temperature

Abstract

Au metalization schemes were deposited on AlGaN/ GaN heterostructures. The dependence of the specific contact resistance on the annealing conditions and the V:Al thickness ratio was shown. For an optimized electrode stack, a low specific contact resistance of 8.9 Â 10 À6 X cm 2 was achieved at an annealing temperature of 650 C. Compared to the conventional Ti/Al/Ni/Au contact, this is a reduction of 150 K. The microstructure and contact formation at the AlGaN/metal interface were investigated by transmission electron microscopy including high-resolution micrographs and energy dispersive X-ray analysis. It was shown that for low-resistive contacts, the resistivity of the metalization has to be taken into account. The V:Al thickness ratio has an impact on the formation of different intermetallic phases and thus is crucial for establishing ohmic contacts at reduced annealing temperatures. V

Charge density and bare surface barrier height in GaN/AlGaN/GaN heterostructures: A modeling and simulation study

“…Detailed and complete microscopic modeling of these parameters is therefore called for, and will be pursued by us in future. Figure compares our model for the 2DEG charge density with several experimental data . Our model clearly shows a semiquantitative consistency with the modest amount of available experimental data.…”

“…Figure 2 compares our model for the 2DEG charge density with several experimental data. 7,[12][13][14] Our model clearly shows a semiquantitative consistency with the modest amount of available experimental data. We can certainly predict the depletion of the 2DEG density in the AlGaN/ GaN interface with increasing GaN cap thickness.…”

“…The variation of the 2DEG concentration in a GaN/AlGaN/GaN heterostructure with GaN cap thickness is shown. The hall experimental data for m = 32% and d AlGaN = 20 nm, m = 22% and d AlGaN = 23.4 nm, m = 30% and d AlGaN = 30 nm, and m = 23% and d AlGaN = 17 nm, are also shown as dots…”

“…Equation (2)) are 1.118Á10 13 , 1.046Á10 13 , and 0.963Á10 13 cm −2 , respectively, showing a good agreement. Figure 4 compares our BSBH model with the simulation results for different sets of m and d AlGaN over a range of 13 and m = 23% and d AlGaN = 17 nm, 14 are also shown as dots FIGURE 3 The variation of the 2DEG concentration in a GaN/AlGaN/ GaN heterostructure with GaN cap thickness is shown. The hall experimental data are shown as dots for m = 100% and d AlGaN = 3.5 nm, 8 for m = 100% and d AlGaN = 3 nm, 15 for m = 53% and d AlGaN = 5.7 nm 16 d cap,GaN .…”

Microanalysis of the Ti/Al and Ti/Al/Mo/Au ohmic contacts metallization to AlGaN/GaN heterostructures

“…In literature there are several works related to Ti/Al based ohmic contacts to AlGaN/GaN heterostructures where a different crystalline quality and various process parameters such as surface cleaning procedure, annealing conditions were investigated . There are attempts of fabrication of Al‐free ohmic contacts , but ohmic contacts based on Ti/Al bilayer annealed above 800 °C are still typically used to achieve low‐resistance ohmic contacts to AlGaN/GaN heterostructures.…”