SIMS quantification of matrix and impurity species in AlxGa1−xN
Introduction
New applications in optoelectronic devices and high power electronic devices continue to be developed using AlxGa1−xN. Due to the material's wide band gap range, the AlxGa1−xN's are very attractive materials for applications in ultraviolet (UV) laser diodes (LD's), light emitting diodes (LED's) and photo detectors [1]. The large band gap, large electric field breakdown and good thermal/chemical stability make AlxGa1−xN semiconductors the materials of choice for high power, high temperature electronic devices [2].
The properties of AlxGa1−xN materials are strongly influenced by alloy concentration and impurities such as Si, Mg, O, C, H, etc. Thus quantification of matrix and impurity species in AlxGa1−xN is essential for compositional analysis, dopant control, and impurity control. Dynamic SIMS is commonly used for the quantification of AlxGa1−xN due to its capability of providing in-depth profiles with high sensitivity and good depth resolution. However, quantification in AlxGa1−xN can be challenging because of matrix and charging effects. The secondary ion yields of matrix and impurity species vary in AlxGa1−xN with different AlN mole fraction. Sample charging which increases with AlN mole fraction must also be dealt with, particularly in the case of undoped AlxGa1−xN alloys having x > 0.4 [3]. In this work, a SIMS quantification method is developed for the AlxGa1−xN system over the range of x = 0 to 1.
Section snippets
Experiment
A set of AlxGa1−xN films with x ranging from 0 to 0.58 were grown using metal organic chemical vapor deposition (MOCVD). The AlN mole fraction of the AlxGa1−xN films was determined using Low Energy X-Ray Emission Spectroscopy (LEXES). These films were implanted with 24Mg at 120 keV to a dose of 2E14 at./cm2 and 29Si at 150 keV to a dose of 5E14 at./cm2. In order to extend the sample set to include an AlN mole fraction close to but not equal to 1, an AlN sample was implanted with 150 keV 1E17 at./cm2
Sputter rate
Sputter rates normalized to primary ion intensity obtained for the SIMS analytical conditions described above for the AlxGa1−xN samples are presented in Fig. 1. The sputter rates decrease with increasing AlN mole fraction x, which is similar to the result previously reported for AlxGa1−xAs [6]. Although the increase in the Cs+ sputter rate for the 5.5 keV (10 kV primary ion/4.5 kV sample bias) versus the 14.5 keV impact energy (10 kV primary ion/−4.5 kV sample bias) may appear counter intuitive, the
Summary
Using the sputtering conditions presented in this study, the sputter rate decreases with x in AlxGa1−xN. In the range of 0 < x < 0.58, the matrix ion intensity ratios appear to increase linearly with matrix mole fraction or mole fraction ratio. When plotted inversely, the linear correlation appears to increase to 0.39 < x < 1. The overlap of these linear ranges allows quantification of matrix elements over the entire range of AlxGa1−xN's (0 < x < 1) under these analytical conditions.
The RSF's for Si and Mg
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Detection of Si doping in the AlN/GaN MQW using Super X – EDS measurements
2020, MicronCitation Excerpt :The result of SIMS measurement was presented in Fig. 11 In this study, we experimentally investigate and next calculate the Si doping for the GaA/AlN:Si material using the GaN standard. The relative sensitivity factors (RSF) for Si was calculated by normalizing to selected Ga matrix ions Ga+ and then recalculated as authors demonstrated in (Gu et al., 2006) taking into account the matrix composition as Al0.4 Ga0.6N. The obtained value of Si concentration by the SIMS method is overestimated, which is associated with the RSF factor and probably with recalculations to the standard.
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