Density Functional Theory Study on Defect Behavior Related to the Bulk Lifetime of Silicon Crystals for Power Device Application

Among the insulated‐gate bipolar transistors (IGBTs) and PIN junction diodes, there are devices that the recombination centers, namely lifetime‐control defects, are introduced into phosphorus (P) doped n‐type silicon (Si) crystals by electron beam irradiation. The lifetime‐control defects are considered as they form deep levels such as the vacancy–vacancy (V–V) pair and vacancy–phosphorus (V–P) pair. In the case of using Czochralski Si wafers, it is considered that some pairs of carbon (C), oxygen (O), and their complexes are believed to have a negative impact to the lifetime‐control defects. In this study, density functional theory (DFT) calculations are performed to understand the formation behavior of lifetime‐control defects and the formation behavior of complexes composed of C and O atoms believed to interact with lifetime‐control defects. On the basis of these results, DFT calculations related to the structural change of lifetime‐control defects are performed. The most important result is that instead of the interstitial carbon–substitutional carbon (Ci–Cs) pair, the interstitial Ci atom and interstitial carbon–interstitial oxygen (Ci–Oi) pair are the strong candidates to affect controllability of lifetime by interacting with V composed of lifetime‐control defects. Not interstitial carbon‐substitutional carbon (Ci–Cs) pair but interstitial Ci atom and interstitial carbon‐interstitial oxygen (Ci–Oi) pair are the strong candidates to affect controllability of lifetime by interacting with vacancy V composed of lifetime‐control defects. Ci and Ci of Ci–Oi interact with V and become Cs.