High efficient photoluminescence from isoelectric impurities in quantum confined Si nanocrystals

本工作的目的是通过同时掺杂n型和p型杂质在Si纳米晶体中形成等电阱。我们开发了一种制备P和B共掺杂Si纳米晶体的方法，并详细研究了P和B浓度对其光学性质的影响。载流子补偿的Si纳米晶体的光致发光强度大于n型或p型杂质掺杂的Si纳米晶体，有时甚至大于纯Si纳米晶体。此外，光致发光能量的可调范围扩展到块体硅晶体的带隙能量以下。通过适当控制Si纳米晶的杂质浓度和尺寸，光致发光能量控制在0.9eV到1.5eV之间，而强度损失并不大。载流子补偿的硅纳米晶体也作为稀土离子的有效光敏剂。研究表明，载流子补偿的硅纳米晶体可以有效地激发放置在其附近的铒离子。铒离子在载流子补偿的硅纳米晶体中的光致发光强度大于纯硅纳米晶体。虽然我们可以成功地证明在Si纳米晶体中形成等电中心是可能的，并且这些纳米晶体表现出纯Si纳米晶体所没有的特征，但掺杂杂质的Si纳米晶体的电子结构仍然没有完全阐明。为了扩展硅纳米晶体的功能和探索其应用，深入了解其电子结构是必不可少的，也是未来研究的目标。

The purpose of this work is to form an isoelectric trap in Si nanocrystals by simultaneously doping n and p type impurities. We have developed a method to prepare P and B codoped Si nanocrystals, and studied the optical properties in detail as functions of P and B concentration. The photoluminescence intensity of carrier-compensated Si nanocrystals was larger than that of either n or p type impurity doped Si nanocrystals, and sometimes it was larger than that of pure Si nanocrystals. Furthermore, the tunable range of photoluminescence energy is extended to below the bandgap energy of bulk Si crystals. By properly controlling the impurity concentration and size of Si nanocrystals, the photoluminescence energy was controlled from 0.9eV to 1.5eV without losing the intensity so much. The carrier compensated Si nanocrystals also act as an efficient photo-sensitizer for rare-earth ions. It has been demonstrated that the carrier compensated Si nanocrystals can excite Er ions placed nearby quite efficiently. The photoluminescence intensity of Er ions in carrier-compensated Si nanocrystals was larger than that in pure Si nanocrystals.Although we could successfully demonstrate that the formation of isolectric centers in Si nanocrystals is possible and these nanocrystals exhibit characteristic features, which are absent in pure Si nanocrystals, the electronic structures of impurity doped Si nanocrystals are still not fully clarified. In order to extend the functionality of Si nanocrystals and explore the applications, deeper understanding of the electronic structures is indispensable, and will be a target of future research.