n-type doping of CuInSe2 and CuGaSe2 -: art. no. 035211
n-type doping of CuInSe2 and CuGaSe2 -: art. no. 035211
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DOI：
10.1103/physrevb.72.035211
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发表时间：
2005-07-01
影响因子：
3.7
通讯作者：
Zunger, A
中科院分区：
文献类型：
--
作者：
Persson, C;Zhao, YJ;Zunger, A
如果将 CuGaSe2（一种带隙更宽的黄铜矿半导体）添加到 CuInSe2 吸收层中，则基于 CuInSe2 的太阳能电池器件的效率可以显着提高。然而，这受到 n 型 CuGaSe2 掺杂难度的限制，因此，在其合金中掺杂 CuInSe2 也很困难。事实上，半导体系列的较宽能隙成员通常比同系列的较低能隙成员更难掺杂。我们发现在黄铜矿中，控制 n 型掺杂的费米能 E-F 存在三个临界值：(i) E-F(n,pin) 是形成 Cu 空位的能量为零时的 E-F 值。此时，自发形成的空位（=受体）杀死所有电子。 (ii) E-F(n,comp) 是 E-F 的值，其中形成 Cu 空位的能量等于形成 n 型掺杂剂（例如 Cd-Cu）的能量。 (iii) E-F(n,site) 是 E-F 的值，其中 Cd-on-In 的形成量等于 Cd-on-Cu 的形成量。为了获得良好的 n 型掺杂，E-F(n,pin)、E-F(n,comp) 和 E-F(n,site) 的间隙需要尽可能高。我们发现这些量在CuInSe2中的能隙中比在CuGaSe2中更高，因此后者难以n型掺杂。在这项工作中，我们计算了所有三个临界费米能，并从理论上研究了具有可能的阳离子和阴离子掺杂的 n 型 CuInSe2 和 CuGaSe2 的最佳生长条件。我们发现 V-Cu 和 In-Cu 或 Ga-Cu 等本征缺陷在两种黄铜矿的掺杂中发挥着重要作用。对于 II 族阳离子（Cd、Zn 或 Mg）掺杂，最佳的 n 型生长条件是富 In/Ga，最大贫 Se，这也是稳定本征 In-Cu/Ga-Cu 供体的最佳条件。块状 CuInSe2 可以以平衡 n 型掺杂，但块状 CuGaSe2 不能掺杂，因为本征铜空位的形成能较低。对于卤素阴离子掺杂，最好的 n 型材料生长仍然是在富 In/Ga 和最大贫 Se 条件下。这些条件对于卤素替代缺陷来说并不是最佳的，但对于本征 In-Cu/Ga-Cu 供体来说是最佳的。同样，CuGaSe2 不能通过卤素掺杂实现 n 型掺杂，而 CuInSe2 可以。
The efficiency of CuInSe2 based solar cell devices could improve significantly if CuGaSe2, a wider band gap chalcopyrite semiconductor, could be added to the CuInSe2 absorber layer. This is, however, limited by the difficulty of doping n-type CuGaSe2 and, hence, in its alloys with CuInSe2. Indeed, wider-gap members of semiconductor series are often more difficult to dope than lower-gap members of the same series. We find that in chalcopyrites, there are three critical values of the Fermi energy E-F that control n-type doping: (i) E-F(n,pin) is the value of E-F where the energy to form Cu vacancies is zero. At this point, the spontaneously formed vacancies (=acceptors) kill all electrons. (ii) E-F(n,comp) is the value of E-F where the energy to form a Cu vacancy equals the energy to form an n-type dopant, e.g., Cd-Cu. (iii) E-F(n,site) is the value of E-F where the formation of Cd-on-In is equal to the formation of Cd-on-Cu. For good n-type doping, E-F(n,pin), E-F(n,comp), and E-F(n,site) need to be as high as possible in the gap. We find that these quantities are higher in the gap in CuInSe2 than in CuGaSe2, so the latter is difficult to dope n-type. In this work, we calculate all three critical Fermi energies and study theoretically the best growth condition for n-type CuInSe2 and CuGaSe2 with possible cation and anion doping. We find that the intrinsic defects such as V-Cu and In-Cu or Ga-Cu play significant roles in doping in both chalcopyrites. For group-II cation (Cd, Zn, or Mg) doping, the best n-type growth condition is In/Ga-rich, and maximal Se-poor, which is also the optimal condition for stabilizing the intrinsic In-Cu/Ga-Cu donors. Bulk CuInSe2 can be doped at equilibrium n-type, but bulk CuGaSe2 cannot be due to the low formation energy of intrinsic Cu-vacancy. For halogen anion doping, the best n-type materials growth is still under In/Ga-rich, and maximal Se-poor conditions. These conditions are not best for halogen substitutional defects, but are optimal for intrinsic In-Cu/Ga-Cu donors. Again, CuGaSe2 cannot be doped n-type by halogen doping, while CuInSe2 can.