Hydrogen-induced Nitrogen Passivation in Dilute Nitrides: A Novel Approach to Defect Engineering
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0994-F02-08
Hydrogen-induced Nitrogen Passivation in Dilute Nitrides: A Novel Approach to Defect Engineering Rinaldo Trotta1, Antonio Polimeni1, Marco Felici1, Giorgio Pettinari1, Mario Capizzi1, Andrea Frova1, Giancarlo Salviati2, Laura Lazzarini2, Nicola Armani2, Luigi Mariucci3, Giorgio Bais4, Faustino Martelli4, and Silvia Rubini4 1 Dipartimento di Fisica, Sapienza Universita' di Roma, P.le A. Moro 2, Roma, 00185, Italy 2 IMEM-CNR, Parco Area delle Scienze 37/A, Localita' Fontanini, Parma, 43010, Italy 3 IFN-CNR, Via Cineto Romano 42, Roma, 00156, Italy 4 TASC INFM-CNR, Parco Area delle Scienze, Trieste, 34012, Italy
ABSTRACT The capability of hydrogen to passivate nitrogen in dilute nitrides is exploited to in-plane engineer the electronic properties of Ga(AsN)/GaAs heterostructures. Two methods are presented: i) by deposition of hydrogen-opaque metallic masks on Ga(AsN) and subsequent hydrogen irradiation, we artificially create zones of the crystal having the band gap of untreated Ga(AsN) surrounded by GaAs-like barriers; ii) by employing an intense (~100 nA) and narrow (~100 nm) beam of electrons, we dissociate the complexes formed by N and H in a spatially delimited part of a hydrogenated Ga(AsN) sample. As a consequence, in the spatial regions irradiated by the electron beam, hydrogenated Ga(AsN) recovers the smaller energy gap it had before hydrogen implantation.
INTRODUCTION In elemental or compound semiconductor crystals, the substitution of a given percentage of atoms with suitable isovalent elements usually alters the electronic properties of the host crystal in a predictable way [1]. This boosted the use of semiconductors in an endless number of applications and devices. The incorporation of N in GaAs or (InGa)As leads, instead, to unpredicted and rather counterintuitive alloy phenomena [2]. These latter comprise a giant reduction in the band gap energy [3] and a deformation of the conduction band structure [4], giving rise to a puzzling compositional dependence of the parameters governing transport (i. e., electron mass) [5-7] and spin-related (i. e., electron g-factor) [8] properties of the Ga(AsN) alloy. These phenomena originate from the interaction of the GaAs extended states with electronic localized levels related to single and multiple N complexes (e. g., pairs, triplets, and clusters) [9,10]. The peculiar properties of Ga(AsN) and (InGa)(AsN) materials (referred to as dilute nitrides) have high potential for telecommunications through optical fibers [11], multi-junction solar cells [12], heterojunction bipolar transistors [13], and terahertz applications [14]. Ga(AsN) and (InGa)(AsN) exhibit even more surprising effects when irradiated with hydrogen. In conventional semiconductors, hydrogen was largely investigated by virtue of its extraordinary capability to saturate dangling bonds and hence to improve the optical and electrical properties of several materials [15]. Additionally, H acts as a dopant in ZnO [16,17] as
well as an efficient impurity neutralizer in GaAs [18,19] and GaN [20,
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