Halide semiconductors stand at the very beginning of semiconductor science and technology. CuI was reported as the first transparent conductor, and the first field effect transistor was made from KBr. Although halogens are frequently used in semiconductor preparation, little use is currently made from halide semiconductors in electronics and photonics. We review past reports on the metal halide semiconductor CuI and related alloys and discuss recent progress with regard to this material including its use in organic electronics and solar cells as well as our own work on fully transparent bipolar heterostructure diodes (p‐CuI/n‐ZnO) with high rectification of several 107 and ideality factors down to 1.5. γ‐CuI(111) thin film on glass (1 × 1 cm2) and IV‐characteristics of p‐CuI/n‐ZnO/a‐Al2O3 bipolar heterojunction diode.

Mg x Zn 1 − x O nanowires with Mg-content x from 0 to 0.2 have been grown by high-pressure pulsed-laser deposition (PLD) on gold-covered sapphire single crystals. The PLD process allows for a unique wide-range control of morphology, diameter, and composition of the MgxZn1−xO nanowires. The diameter of single ZnO wires could be varied between about 50 and 3000 nm, and the Mg content x of MgxZn1−xO wire arrays was controlled via the PLD gas pressure. The microscopic homogeneity of Mg content is displayed by cathodoluminescence (CL) imaging of the excitonic peak energy. The fluctuation of CL peak energy between individual wires is about an order of magnitude smaller than the alloy broadening.

Cuprous iodide has been investigated since 1907 when Karl Bädeker prepared this material from metallic copper thin films with subsequent iodization and reported it as fully transparent conductor. Nowadays CuI is recognized as p‐type wide bandgap, transparent semiconductor, offering rather high hole mobilities of so far up to 10 Vs∕cm2 in thin films. The charge carrier density is primarily controlled via the amount of copper vacancies. CuI has been prepared as bulk material and substrate and thin film as well as in the form of various nanostructures. Thin films can be prepared by various techniques including iodization of copper and by thermal evaporation, sputtering or pulsed laser deposition of CuI. Recent progress is represented by the epitaxy on other semiconductors, in particular zinc oxide. CuI has found use as intermediate layer between ITO and organic absorbers in solar cells. Recently, bipolar heterostructure diodes prepared from p‐CuI∕n‐ZnO layers on sapphire were found to exhibit very high rectification. This makes CuI interesting for use in transparent electronics. For further details see the Review Article by M. Grundmann et al. on pp. http://doi.wiley.com/10.1002/pssa.201329349.

Phosphorus-doped ZnO (ZnO:P) nanowires were successfully prepared by a novel high-pressure pulsed-laser deposition process using phosphorus pentoxide as the dopant source. Detailed cathodoluminescence studies of single ZnO:P nanowires revealed characteristic phosphorus acceptor-related peaks: neutral acceptor-bound exciton emission (A 0 , X, 3.356 eV), free-to-neutral-acceptor emission (e, A 0 , 3.314 eV), and donor-to-acceptor pair emission (DAP, ∼3.24 and ∼3.04 eV). This means that stable acceptor levels with a binding energy of about 122 meV have been induced in the nanowires by phosphorus doping. Moreover, the induced acceptors are distributed homogeneously along the doped nanowires.

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