Composition Metrology of Ternary Semiconductor Alloys Analyzed by Atom Probe Tomography

Abstract

Ternary semiconductor alloys based on the A y B1–y C stoichiometry are widely employed in electronic devices, and their composition plays a key role in band gap engineering of heterostructures. We have studied the crucial issue of accuracy in composition measurements of Al y Ga1–y N and Mg y Zn1–y O alloys using atom probe tomography (APT). The results indicate a similar behavior for both nitride and oxide systems. A correct site fraction y is measured at low field conditions, while Ga and Zn preferentially evaporate at high field, yielding an overestimation of y. Furthermore, APT data sets exhibit local biases depending on the distribution of the electrostatic field at the specimen surface. We estimate the detection efficiencies for each species and interpret the results through a model describing preferential evaporation in simple terms.

Correlative investigation of Mg doping in GaN layers grown at different temperatures by atom probe tomography and off-axis electron holography

“…44 Precedent studies reveal that such field conditions lead measuring a more reliable III-fraction in ternary GaN-based alloys. 15,16,26 This consideration can also be extended to the case of MgGaN, even if a dedicated study have yet to be developed. Therefore, only information from doped layer grown at T growth = 1010 • C to the doped layer grown at T growth = 1090 • C are extracted and compared relatively.…”

“…13,14 This reduces also the preferential loss of metallic species during the tip evaporation and allows to better estimate the Mg fraction. 15,16 The 3D reconstruction was performed using a cone-angle algorithm. As it was not possible to properly reconstruct the entire volume analyzed adopting a unique set of parameters, different sub-volumes containing a single p-doped layer was separately reconstructed.…”

“…Of course, the measured fraction y within a layers is not strictly quantitative and is only used to demonstrate the relative evolution of the composition. 15,16,26 The Mg fraction for both the potentially active Mg atoms in p-doped layers and those detected in the NID layers is shown in Figure 3 Off-axis electron holography technique is a TEM based technique that uses an electron biprism to create an interference pattern known as the hologram. 27 A coherent electron wave that passes through the specimen is interfered with another that passes through vacuum.…”

Multi-microscopy nanoscale characterization of the doping profile in a hybrid Mg/Ge-doped tunnel junction

“…The choice for the mass spectrum peak indexing is the same as the one commonly reported in literature [34][35][36][37][38][39][40][41][42][43][44]. Mg 2+ cations are associated with the peaks at 12, 12.5 and 13 Da, due to its three isotopes ( fig.…”

Behavior of the ε-Ga2O3:Sn Evaporation During Laser-Assisted Atom Probe Tomography

“…Surprisingly, all these studies reveal that APT measures nonstoichiometric compositions with 10% or more variations on the expected value of composition provided by more reliable analytic techniques (i.e., SIMS, RBS) or fixed by the material crystalline structure itself, as in the case of binary semiconductors like GaN or ZnO. Despite the fact that it is well accepted that the intensive standing electric field (in the range of 15–30 V/nm) required to trigger the laser-assisted field emission of cations from the sample surface is the main parameter driving the composition variations measured by APT, further efforts to investigate both the evaporation mechanisms (Gault et al, 2016; Di Russo et al, 2017 a , 2018 a , 2018 b ) and detection limitations (Di Russo et al, 2017 b ) are required for a full understanding of physical mechanisms giving rise to such chemical inaccuracies. This is crucial not only for the potential impact on the technique development, but also to properly tune the analysis parameters and reduce the selective loss of chemical species currently leading to inaccurate composition measurements in semiconductors.…”