Telluroether and Selenoether Complexes as Single Source Reagents for Low Pressure Chemical Vapor Deposition of Crystalline Ga₂Te₃ and Ga₂Se₃ Thin Films

The neutral complexes [GaCl 3 (E n Bu 2 )] (E = Se or Te), [(GaCl 3 ) 2 { n BuE(CH 2 ) n E n Bu}] (E = Se, n = 2; E = Te, n = 3), and [(GaCl 3 ) 2 { t BuTe(CH 2 ) 3 Te t Bu}] are conveniently prepared by reaction of GaCl 3 with the neutral E n Bu 2 in a 1:1 ratio or with n BuE(CH 2 ) n E n Bu or t BuTe(CH 2 ) 3 Te t Bu in a 2:1 ratio and characterized by IR/Raman and multinuclear ( 1 H, 71 Ga, 77 Se{ 1 H}, and 125 Te{ 1 H}) NMR spectroscopy, respectively, all of which indicate distorted tetrahedral coordination at Ga. The tribromide analog, [GaBr 3 (Se n Bu 2 )], was prepared and characterized similarly. A crystal structure determination on [(GaCl 3 ) 2 { t BuTe(CH 2 ) 3 Te t Bu}] confirms this geometry with each pyramidal GaCl 3 fragment coordinated to one Te donor atom of the bridging ditelluroether, Ga–Te = 2.6356(13) and 2.6378(14) Å. The n Bu-substituted ligand complexes serve as convenient and very useful single source precursors for low pressure chemical vapor deposition (LPCVD) of single phase gallium telluride and gallium selenide, Ga 2 E 3, films onto SiO 2 and TiN substrates. The composition and morphology were confirmed by SEM, EDX, and Raman spectroscopy, while XRD shows the films are crystalline, consistent with cubic Ga 2 Te 3 ( F 4̅3 m ) and monoclinic Ga 2 Se 3 ( Cc ), respectively. Hall measurements on films grown on SiO 2 show the Ga 2 Te 3 is a p-type semiconductor with a resistivity of 195 ± 10 Ω cm and a carrier density of 5 × 10 15 cm –3, indicative of a close to stoichiometric compound. The Ga 2 Se 3 is also p-type with a resistivity of (9 ± 1) × 10 3 Ω cm, a carrier density of 2 × 10 13 cm –3, and a mobility of 20–80 cm 2 /V·s. Competitive deposition of Ga 2 Te 3 onto a photolithographically patterned SiO 2 /TiN substrate indicates that film growth onto the conducting and more hydrophobic TiN is preferred.