Design Principles of p-Type Transparent Conductive Materials

Abstract

Transparent conductive materials (TCMs) has always been playing a significant role in electronic and photovoltaic area, due to its prominent optical and electronic properties. To render those transparent materials highly conductive, efficient n-and p-type doping is critically needed to obtain high concentration of free electron and hole carriers. Despite extensive research over the past five decades, highquality p-type doping of wide-band-gap transparent materials remains a challenge. Here, we summarize four proposed design principles to enhance the p-type conductivity of these wide band gap materials, including (i) reducing the formation energy of the acceptors to enhance the dopant concentration; (ii) lowering the ionization energy and, hence, increasing the ionization of the acceptors to increase the concentration of the free holes; (iii) increasing the VBM of the host material to approaching the pinned Fermi level; and (iv) suppressing the compensating donors to shifting the pinning Fermi level toward the VBM. For each mechanism, we discuss in detail its underlying physics and provided some examples to illustrate the design principles. From this review, one could learn the doping principles and have a strategic mind when designing other p-type materials.

Extrinsic Photoconduction Induced Short‐Wavelength Infrared Photodetectors Based on Ge‐Based Chalcogenides

“…All atoms were allowed to relax until the force on each atom was less than 0.02 eV. For supercell calculations on point defects, the formation energy is given by [ 56 ] where E (host) and E (α, q ) are the total energies of the perfect host system and the supercell containing the defect α in charge state q , respectively; E ( i ) is the energy of elemental solid or gas; μ i is the chemical potential of elemental species i referenced to E ( i ) and n i indicates the number of atoms added (negative sign) or removed (positive sign) from the supercell model. ε F represents the Fermi level and ε VBM (host) is the valence band maximum (VBM) of the host system.…”

“…All atoms were allowed to relax until the force on each atom was less than 0.02 eV. For supercell calculations on point defects, the formation energy is given by [56] E q E q E n E i n q q…”

Defect physics and doping engineering in semiconductor optoelectronic materials

“…同理, 导带底能量越高, 就越难进行n型掺 杂 [7] , 此即掺杂极限定律. 基于该定律, 我们总结了提 高氧化物宽禁带半导体p型掺杂的缺陷调控方案 [28] , 既 要降低受主离化能, 又要抑制补偿施主缺陷的形成. 降 低受主离化能主要有以下几种方式: [29] ;…”

Comparing metal oxide thin films as transparent p-type conductive electrodes

“…For the best design of p-type TCOs, both experimental and theoretical data about the electronic structure of metal oxides should be taken into account [7][8][9]. In most metal oxides, the minimum of the conduction band (CBM) is formed by metallic s orbitals that are spatially extended.…”

“…On the other hand, the maximum of the valence band (VBM) is formed by oxygen 2p orbitals, which are quite localized, giving rise to a large effective mass for holes that results in very low mobilities for these charge carriers. Furthermore, the dispersion of the valence band tends to be small, and the VBM level is so deep that p-type doping is difficult [9].…”