Energy spike effects in ion-bombarded GaN

Abstract

We study structural disorder in GaN bombarded at room temperature with 1.3 keV amu−1 PFn (n = 0, 2 and 4) cluster ions. Results are compared with our previous studies of irradiation with atomic ions of different masses. An algorithm for cascade density calculations that take into account the formation of subcascades is presented. Quantitative analysis of both new and previous data shows that an increase in the cascade density above a certain critical value results in a rapid increase in the rate of planar amorphization and the rate of damage buildup in the crystal bulk. Both such rates increase with decreasing sample temperature. This threshold-like behaviour suggests an important role of nonlinear energy spikes in the formation of stable implantation disorder in GaN. We also discuss the striking difference between cascade density effects in damage buildup in different semiconductors, including GaN, ZnO and Si.

Atomistic simulation of damage production by atomic and molecular ion irradiation in GaN

“…The cascade density effect during ion irradiation was studied by maintaining the following parameter constant: ion energy normalized to ion mass, ion dose normalized to the number of displacements per atom (DPA) and ion beam flux normalized to DPAs −1 [14,85]. Here, DPA= Φ× g v /n at , where Φ is ion dose, g v is the SRIM [86] calculated number of ion-beam-generated lattice vacancies at the maximum of the nuclear energy loss profile, and n at is the atomic density of the target.…”

“…This is explained by the overlap of separate cascades composing the cluster of fluorine and phosphorus atoms in a narrow near-surface region to a depth of ∼10-12 nm. between the efficiency of damage buildup and the density of collision cascades where cluster ions produce denser cascades than single ions [14]. In the following, damage production in GaN by single and molecular ion irradiation has been studied by means of atomistic simulation based on the above contexts.…”

“…These observations about light single, molecular and heavy mass ions can be explained based on the cascade density effect on defect formation [14]. Light ions (P and F) produce very dilute collision cascades, so they mainly produce point defects and small clusters.…”

“…However, not many works have been focused on the defect formation behaviour when irradiation is done by molecular projectiles. Some experiments have shown that the damage production itself in semiconductors is non-linear with the deposited energy density of single and molecular projectiles [12][13][14]. There are also experiments investigating the effect of ion-beam-produced defects on luminescence properties [15][16][17][18].…”

Effects of collision cascade density on radiation defect dynamics in 3C-SiC

“…Previous experiments for different materials have revealed that the efficiency of the formation of stable damage generally increases with increasing m 6891013161718193132. However, even the qualitative behavior is non-trivial and depends strongly on the material and irradiation conditions such as Φ, F , and T .…”