Effect of silicon and oxygen doping on donor bound excitons in bulk GaN

Abstract

Freestanding n-type intentionally doped GaN layers grown by halide vapor phase epitaxy (HVPE) were studied by transient photoluminescence (PL). Concentrations of silicon and oxygen were varied in the range between 10 17 and 10 18 cm −3 , as confirmed by secondary ion mass spectroscopy (SIMS). We show that a reduction of the background silicon concentration by one order of magnitude compared to the background level in undoped samples can be achieved by incorporation of oxygen during the growth. A strong band gap narrowing (BGN) of ∼6 meV was observed with increasing doping in the studied samples. The low temperature PL recombination time for donor-bound excitons (DBEs) was found to depend significantly on donor concentration. A model assuming generation of DBEs by capturing of free excitons by neutral donors explains the experimental results at low temperature. From fitting the experimental DBE lifetime to the model, the donor concentration dependence for O and Si donors could be reproduced. An effective exciton capture cross-section was found to be ∼9.4 × 10 −15 and 1.2 × 10 −14 cm 2 for silicon and oxygen donors, respectively.

Optical properties of C-doped bulk GaN wafers grown by halide vapor phase epitaxy

“…18 To obtain SI, GaN material iron has been used as a suitable dopant. Fe can substitute Ga upon which it acts as a compensating deep acceptor.…”

Study of optical properties of bulk GaN crystals grown by HVPE

“…Some studies on GaN have claimed that carbon-related defects are important sources of deep states responsible for the YL band in GaN [10e14] because C impurities will be introduced in a metalorganic chemical vapor deposition (MOCVD) process as the main impurity in GaN [15,16]. Meanwhile, a correlation between the YL band and the concentration of O impurities has also been reported [17,18], indicating that the YL band is attributed to transitions from the O donor to a deep acceptor [19]. In addition, the YL band of GaN is also attributed to some native defects.…”

Hopping conduction and piezoelectricity in Fe-doped GaN studied by non-contacting resonant ultrasound spectroscopy

“…The Arrhenius plot yields the activation energy of the hopping conduction to be 0. 23 Fe ions have been doped in gallium nitride (GaN) as deep acceptors for compensating n-type carriers to achieve a semi-insulating GaN, [1][2][3][4] which is a key material in various electric devices such as a high-electron-mobility transistor (HEMT). 1,[5][6][7] The device performances, however, deteriorate with increasing temperature.…”

“…Because the HVPE method introduces many donors mainly from silicon and oxygen, 23 Fe ions were introduced to compensate them. 3,24 The resistivity at room temperature and Fe concentration are 2 Â 10 8 X cm and 8 Â 10 18 cm À3 , respectively.…”