Berthelot-type optical and electrical properties of InGaN/GaN multiple quantum well p-i-n heterostructures composed of InGaN/ GaN multiple quantum barriers with different InN molar fraction have been systematically investigated. Indium incorporation in the nanostructures augmented the increase in crystalline randomization. The so-called Berthelot behavior was observed, that is, the EL peak energy of the blue emission increased with temperature and then decreased monotonically. The electrical conductances of these samples were also contingent on the Berthelot temperatures. The thermal-related characterization for the spectral and transport measurement both corroborated that the Berthelot-type response was attributed to the microstructure disordering arising from the In nonstoichiometry. (c) 2005 Elsevier B.V. All rights reserved.