Observation of the Metal-Insulator Transition in Two-Dimensional n-type   GaAs
  The observation of a carrier-density driven metal-insulator transition in n-type GaAs-based heterostructure is reported. Although weaker than in comparable-quality p-type GaAs samples, the main features of the transition are rather similar. 
Y. Hanein, D. Shahar, J. Yoon, C.C. Li, D.C. Tsui and Hadas Shtrikman