Phase equilibria in In-Metal-As systems: Systematic trends in phase diagram topology and implications for the development of contact materials to InAs

Design of thermally stable gate metallizations for AlGaAsSb/InAs HEMTs

“…It was determined via energy dispersive spectroscopy (EDS) that the isolated grains consist mostly of indium, and titanium arsenide was found directly above the isolated grains after 15 h of ageing. This finding is consistent with prior work of Swenson that reports that TiAs is in thermodynamic equilibrium with In and InAs [7]. Nevertheless, cross-sectional TEM verified that Ti is a good candidate for making a thermally stable gate metallization on InAs due to a slow reaction rate.…”

“…W/Au (100/100 nm) gate metallizations are found to be good candidates for making thermally stable gate metallizations on AlGaAsSb without the InAs cap. Comparing W/Au (30/100 nm) and W/Au (100/100 nm), an addition of 70 nm to the tungsten barrier gives a longer lifetime at 250 • C, which is in agreement with the thermodynamic prediction that W is in equilibrium with AlSb [7] and its known effectiveness as a diffusion barrier. An order of magnitude increase in the currents at −0.2 V was observed after the W/Au (100/ 100 nm) gate metallizations were aged at 250 For the ageing of gates on AlGaAsSb with the InAs cap, the I-V characteristics of Ti/Pt/Au (30/40/80 nm) gate metallizations remained nearly unchanged after ageing for 8 h. However, more than one order of magnitude increase in the current at −0.2 V was observed after ageing for 14 h, as shown in figure 4.…”

“…The reason for the alternating layers was ease of deposition. Similarly, W/Au metallization was examined because W is predicted as thermally stable with InAs [7]. The gate metallizations were held at 250 • C to examine stability during packaging, and to accelerate ageing to learn about long-term stability during operation.…”

“…To design a thermally stable gate metallization, thermodynamics can be used to predict metals that are not reactive on InAs or Al 0.80 Ga 0.20 As 0.16 Sb 0.84 . For the metal-In-As system, Swenson [7] suggested that W, Re, Os, RhIn 3 , PdIn and PtIn 2 are candidates for stable contacts on InAs. In addition, other common metallizations that have high conductivity, such as silicides [8], might be good candidates for making thermally stable contact to InAs.…”