According to the embodiments provided herein, a photovoltaic device can include an absorber layer. The absorber layer can be doped p-type with a Group V dopant and can have a carrier concentration of the Group V dopant greater than 410.sup.15 cm.sup.3. The absorber layer can include oxygen in a central region of the absorber layer. The absorber layer can include an alkali metal in the central region of the absorber layer. Methods for carrier activation can include exposing an absorber layer to an annealing compound in a reducing environment. The annealing compound can include cadmium chloride and an alkali metal chloride.

A photovoltaic device is presented. The photovoltaic device includes a layer stack; and an absorber layer is disposed on the layer stack. The absorber layer comprises selenium, wherein an atomic concentration of selenium varies across a thickness of the absorber layer. The photovoltaic device is substantially free of a cadmium sulfide layer.

An X-ray detector comprises: a semiconductor bulk made of Cd.sub.(1-x)Zn.sub.xTe, wherein x is in a range of 0 to 50%; a contact made of a first material on the semiconductor bulk; and a contact-semiconductor region, which is part of the semiconductor bulk and is adjacent to the contact. The contact-semiconductor region is doped with a second material, which differs from the first material, and a majority of the semiconductor bulk is not doped with the second material.

A substrate to fabricate a photodiode structure has a top layer made from cadmium-doped semiconductor material. A first HgCdTe-base layer is formed by liquid phase epitaxy from the top layer with a bath containing an n-type electrically active dopant to electrically dope the first layer. The cadmium diffuses from the top layer to the first layer to form a decreasing cadmium concentration gradient from the interface with the top layer in a direction away from the interface. The cadmium concentration gradient causes a decreasing band gap width gradient in the first layer from the interface and causes an n-type dopant concentration gradient in the first layer from the interface.

A photovoltaic cell can include an interfacial layer in contact with a semiconductor layer.

Provided are structures and methods for doping polycrystalline thin film semiconductor materials in photovoltaic devices. Embodiments include methods for forming and treating a photovoltaic semiconductor absorber layer.