Strategies for controlling the conductivity of wide-band-gap semiconductors

Wide-band-gap semiconductors have numerous applications in electronic and optoelectronic devices. Progress is currently hampered by a lack of control over electrical conductivity: for instance, ZnO is typically n-type conductive, the cause of which has been widely debated. A first-principles investigation, based on density functional theory, shows that native defects are unlikely to be the cause of the unintentional n-type conductivity. An investigation of likely donor impurities reveals that hydrogen acts as a shallow donor. In contrast, hydrogen acts as an amphoteric impurity in most other semiconductors; calculations for hydrogen in ZnSe are included here to highlight this difference. Experimental results are discussed in light of these new insights.