Text this: Source of two-dimensional electron gas in unintentionally doped AlGaN/GaN multichannel high-electron-mobility transistor heterostructures

__    __    _____               _____    _    _   
\ \\ / //  |  ___||   ____     |  ___|| | |  | || 
 \ \/ //   | ||__    |    \\   | ||__   | |/\| || 
  \  //    | ||__    | [] ||   | ||__   |  /\  || 
   \//     |_____||  |  __//   |_____|| |_// \_|| 
    `      `-----`   |_|`-`    `-----`  `-`   `-` 
                     `-`