Doping dependence of boron-hydrogen dynamics in crystalline silicon

In this contribution, we investigate the formation and dissociation of boron-hydrogen (BH) pairs in crystalline silicon under thermal equilibrium conditions. Our samples span doping concentrations of nearly two orders of magnitude and are passivated with a layer stack consisting of thin aluminum oxide and hydrogen-rich silicon nitride (Al2O3/SiNx:H). This layer stack acts as a hydrogen source during a following rapid thermal annealing. We characterize the samples using low-temperature Fourier-transform infrared spectroscopy and four-point-probe resistivity measurements. Our findings show that the proportion of hydrogen atoms initially bound to boron (BH pairs) rises with increasing boron concentration. Upon isothermal dark annealing at (163 +/- 2) degrees C, hydrogen present in molecular form, H-2, dissociates at a rate directly proportional to the concentration of boron atoms, proportional to [ B-], leading to the formation of BH pairs. With prolonged annealing, an unknown hydrogen complex is formed at a rate that is inversely proportional to the square of the boron concentration, proportional to 1/[B (-)](2), resulting in the disappearance of BH pairs. Based on experimental observations, we derive a kinetic model in which we describe the formation of the unknown complex through neutral hydrogen H-0 binding to a sink. Additionally, we investigate the temperature dependence of the reaction rates and find that the H-2 dissociation process has an activation energy of (1.11 +/- 0.05) eV, which is in close agreement with theoretical predictions.