Rhodium‐based Schottky contacts on n‐doped gallium nitride

Abstract

Electrical characteristics and thermal stability of Rhodium (Rh)‐based Schottky contacts on n‐GaN, including Rh/Au and Ni/Rh/Au, have been investigated and compared with those of the Ni/Au contact. Although the maximum Schottky barrier height (SBH) of the Rh/Au contact is slightly lower than that of Ni/Au, the inclusion of a thin Ni layer to yield the Ni/Rh/Au contact has led to a maximum SBH of 0.80 eV, surpassing that of Ni/Au by 0.07 eV and leading to a reduced reverse leakage current at ‐1 V by 1 order of magnitude com‐ pared to that of Ni/Au. The good performance of the Ni/Rh/Au contact can be attributed to the co‐existence of Rh and a thin layer of Ni, which leads to limited adverse reaction of Ni with the GaN substrate, and formation of NiO and reduced interfacial defects at the metal/GaN interface. In addition, thermal stability studies have shown that Rh‐based contacts exhibit better morphological stability than Ni/Au, and the Ni/Rh/Au contact has improved thermal stability over Rh/Au and Ni/Au contacts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Rhodium pyrazolate complexes as potential CVD precursors

“…We have recently reported RuP amorphous alloys grown utilizing the ruthenium trimethylphosphine complex, cisRuH 2 (PMe 3 ) 4 . 34 The incorporation of phosphorous appears to hinder the formation of crystalline Ru and similar effect is postulated to be taking place here.…”

“…CVD processes can also allow for the selective growth of films that have good step coverage compared with traditional techniques such as PVD. [1][2][3] Thin films of rhodium are used as electrical contacts, 4,5 reflective coatings, 6,7 catalysis, 8,9 and wearresistant coatings for extreme conditions. 2,10 Previous studies have focused on volatile compounds which feature traditional organometallic ligands such as CO, C 2 H 4 , C 5 H 5 , and fluorinated hydrocarbons such as trifluoroacetylacetonate and it has been shown that film quality is dependent on the precursor used.…”

“…Key bond lengths and angles are given in Table 2. Crystallographic details for 1-5 are given in Table 1 4 ] which bears four CO groups. 22 To our knowledge 2 is the first mixed-bridge dinuclear Rh complex that contains bis-trifluoromethyl pyrazolate and PMe 3 ligands.…”

“…Fig. 2 shows the overall molecular geometry and atom numbering scheme for 2 and a listing of key bond lengths and angles is given in 4 ] is 176.0(2)°. In addition the carbonyl complex displays almost no bending between the edge sharing rhodium-ligand planes (angle between planes 145°) and has a Rh-Rh distance of 3.6275(9) Å whereas 2 has an angle of 100°between planes and a Rh-Rh distance of 3.0503(7) Å.…”

“…The structural differences are consistent with computational studies by Lledos and Alvarez who postulated that the angle between planes and metal-metal distances in edge-sharing binuclear square planar d 8 complexes are smaller when good σ-donor ligands are present. 23 Steric interactions may also be involved as 2 contains PMe 3 instead of CO as well as the bis(CF 3 ) substituted pyrazolate instead of unsubstituted Pz in [Rh 2 (μ-Cl)(μ-Pz) (CO) 4 . Solutions of 2 in C 6 D 6 are unstable and there is a slow conversion to a mixture of [Rh(μ-Cl)(PMe 3 ) 2 ] 2 and 4 which takes place over several days.…”