Recent developments in metastable dilute-N III–V semiconductors

Metastable III–N–V semiconductors are a subgroup of a recently discovered new class of III–V and II–VI semiconductor alloys. Band gap engineering is achieved in these alloys by incorporating into a semiconductor host (e.g. GaAs) small amounts of an isoelectronic impurity (e.g. N) whose electronic levels are resonant with the host conduction band. Due to the large differences in size and electronegativity between the impurity and the host anion it substitutes, the band structure of the host is strongly perturbed and modified. The band structure formation of these alloys is totally different from that of conventional amalgamation-type semiconductor alloys such as (Al,Ga)As etc. Exemplarily, this review focuses on Ga(N,As) and (Ga,In)(N,As), which are currently the most prominent III–N–V alloys due to their application in optoelectronic devices. The review addresses electronic structure investigations ranging from bulk epitaxial layers to laser device structures. In particular, the band information process and the band structure of Ga(N,As) are described. Consequences such as the strong correlation between local N environment and global band gap, the metastability of quaternary (Ga,In)(N,As), and strong disorder and localization effects are discussed. Possible ways of parameterizing the band structure in a k·P-like fashion accounting for the effects of nitrogen are presented and employed to describe the electronic states of (Ga,In)(N,As)-based quantum wells. Furthermore, it is shown how (Ga,In)(N,As)/GaAs quantum wells in the active region of vertical-cavity surface-emitting laser structures can be characterized non-invasively.