Beryllium (Be) has been previously shown to be an adequate p-type dopant for molecular beam epitaxy (MBE) grown 0.6 eV n/p/n InGaAs/InPAs double heterostructure thermophotovoltaic (TPV) devices. However, due to environmental, safety, and health operational concerns caused by airborne exposure to Be during cleaning operations in a MBE system, carbon (C) was investigated as a p-type dopant substitute. However, due to the amphoteric nature of C, it incorporates on the group-III site in InGaAsP material with high P content, making it n type. Therefore, to grow the n/p/n InGaAs double heterostructure TPV device, InAlAs was developed as the back surface field (BSF). By using C as the p-type dopant and InAlAs as the BSF, MBE grown 0.6 eV n/p/n InPAs/InGaAs/InAlAs double heterostructure TPV devices were successfully made. The demonstrated room temperature reverse saturation current density (j(0)) value from this MBE grown device was similar to 9 mu A/cm(2). This j(0) value was only three times larger than the previous best MBE grown 0.6 eV n/p/n InGaAs/InPAs double heterostructure TPV device using Be as the p-type dopant. Internal quantum efficiency evidence suggested that, by improving the baseBSF interface for the device having the InAlAs BSF and C p-type doping, j(0) values lower than the previous best MBE grown TPV material were possible. Therefore, C was found to,be a promising alternative to Be in 0.6 eV n/p/n InPAs/InGaAs/InAlAs double heterostructure TPV devices. (c) 2006 American Vacuum Society.