Reactions of Etched, Single Crystal (111)B-Oriented InP to Produce Functionalized Surfaces with Low Electrical Defect Densities

Synthetic routes have been developed that allow attachment of a variety of functional groups to etched, single-crystal InP surfaces. Benzyl halides, alkyl halides, silyl halides, and esters reacted readily with InP to yield covalently attached overlayers on the semiconductor surface. High-resolution X-ray photoelectron spectroscopy (XPS) revealed that the functionalization chemistry was consistent with the reactivity of surficial hydroxyl groups. Analysis of the XP spectra of the (111)B-oriented (P-rich) face in ultrahigh vacuum revealed signals ascribable to a monolayer of oxidized P atoms on the etched (111)B InP surface. The lack of reactivity of the (111)A-oriented (In-rich) face with these same functionalization reagents is therefore attributed to the difference in the nucleophilicity and acidity of the In and P oxides that are present on the (111)A and (111)B faces, respectively. The coverage of benzylic groups obtained through functionalization of (111)B-oriented InP with benzyl halides was estimated to be 4 × 10¹⁴ cm². This coverage implies that the functionalization can only proceed at alternate surface P atom sites in this system, which is expected from molecular packing considerations of these particular functional groups. Photoluminescence decay measurements were performed to investigate the electrical properties of the etched and modified InP surfaces, and these data indicated that the surface recombination velocity of the functionalized InP surface was ≈10² cm s^-1. This low surface recombination velocity implies that 5 atoms on the modified InP surface, indicating that high electrical quality can be maintained while introducing a variety of chemical functionalities onto the (111)B surface of InP.