Carcinoembryonic antigen (CEA) is a well-known biomarker and validated serum biomarker for lung cancer. We introduce a simple label-free method for CEA detection. Specific recognition of CEA was made possible by immobilizing CEA antibodies in the sensing region of AlGaN/GaN high-electron-mobility transistors. The biosensors have a detection limit of 1 fg ml(-1) in phosphate buffer solution. This approach has advantages of integration, miniaturization, low cost, and rapid detection compared to other testing methods for lung cancer and could be used in future medical diagnostics.