Dissociation energies of shallow-acceptor-hydrogen pairs in silicon

Abstract

The thermal dissociation of electrically neutral shallow-acceptor-hydrogen complexes (AH with A B, Al, Ga, and In) follows first-order kinetics over the entire annealing process, provided the isothermal anneals are performed with a reverse bias applied to the Schottky diode. The firstorder kinetics permit a precise determination of the dissociation frequency v& of the acceptorhydrogen pairs. The temperature-dependent values of vz satisfy the relation vz vo&exp( -Ez/ kT), with vos 2.8X 10' s ', voA~3. 1X10' s ', voo, 6. 9X10'3 s ', and vot"8. 4X10' s The dissociation energies E& depend only weakly on the acceptors: Es (1.28+ 0.03) eV, EA/ (1.44~0 02) eV, Eo, (1.40+'0 03) eV, and Et"(1. 42~0 05) eV. Atomic hydrogen introduced into crystalline silicon leads to a deactivation of the group-III shallow acceptors (8, Al, Ga, In, and Tl), due to the formation of an electrically neutral acceptor-hydrogen complex (AH). ' Despite intensive investigations of the structural and electrical properties of the AH complex, ' there are no reliable data on the dissociation energies E~of these pairs. The values of E~reported in the literature show a considerable scatter, ' and strongly depend on the method of hydrogenation. A precise knowledge of E~would provide an additional criterion to check the various microscopic configurations of the AH complexes proposed in the literature. ' Furthermore, an understanding of the dissociation kinetics of the AH complexes facilitates the quantitative analysis of low-temperature (T (200' C) diffusion experiments, where the hydrogen-acceptor interaction strongly modifies the H-diffusion profiles, ' and hampers a precise determination of the H diffusivity.We show that annealing of hydrogenated p-type silicon with a reuerse bias applied to a Schottky diode leads to a reactivation of the acceptor, which follows first-order kinetics throughout the entire time of annealing. The firstorder reactivation of the acceptor in the space-charge region is determined only by the dissociation frequency võ f the complex AH. From the temperature dependence of v~, we obtain the dissociation energies of the various AH pairs (A 8, Al, Ga, and In).We use 8-doped (100) float-zone silicon, Al-or Gadoped (111) Czochralski silicon, and In-doped (111) fioat-zone silicon of 10 0 cm resistivity. The samples are exposed to a radio-frequency (13 MHz) hydrogen plasma for 2 h at temperatures in the range of 120-250'C. A layer of thickness d (d 2-4 pm) below the irradiated surface is then chemically removed, and titanium Schottky contacts (1 mm diam) are evaporated. The Ohmic contact consists of an indium-gallium alloy scratched onto the back surface. Anneals at a temperature T, in the range 40-220'C with a reverse-bias Vtt applied to the Schottky diode are performed in a cryostat under ambient atmosphere. After annealing for a time T"the temperature is rapidly decreased by immersing the sample holder in liquid nitrogen with the bias on. Capacitance versus voltage [C(V)1 measurements at 1 MHz and 14 15xlQ

Annealing kinetics of vacancy-related defects in low-dose MeV self-ion-implantedn-type silicon

“…For instance, atomic hydrogen and the boron acceptor form readily a complex with an estimated dissociation energy in excess of 1.3 eV. 65 Thus, the p ϩ layer acts as an efficient diffusion barrier for hydrogen, explaining the high temperatures needed to observe the interaction between H and VO in the p ϩ /n FZ samples. In the simulations, this is taken into account by introducing a thermally activated injection rate of hydrogen from the p ϩ layer into the n region, ⌰ BH ϭ5ϫ10 12 exp͓Ϫ2 (eV)/kT͔ s…”

Universal alignment of hydrogen levels in semiconductors and insulators

“…In other words, hydrogen is amphoteric: it acts as a donor (H + ) in p-type material, and as an acceptor (H − ) in n-type material, always counteracting the prevailing conductivity. This behavior of hydrogen was confirmed and described in great detail with a variety of experimental techniques [8][9][10][11]. In parallel, theory and computation [12][13][14][15] elucidated the physics of hydrogen's interactions with semiconductors, and established the correlation between its atomic and electronic structure.…”

Hydrogen in crystalline semiconductors

“…This work was stimulated not only by the hydrogen related findings but al~o in part by the well established passivation of acceptors by Li (14); an effect which had been used extensively for many years in the fabrication of large volume lithium drifted germanium gamma ray detectors (28) and lithium drifted SiX-ray and particle detectors, (29) and by the very recent observation that boron and other shallow acceptors are ,passivated in Si by polishing wafers (30). The theoretical findings together with perturbed angular correlation (PAC) position decay experiments (31) and additional experimental evidence (32) show that polishing related passivation is not hydrogen related but most likely due to rapidly diffusing interstitial copper.…”