Effect of dopant profile on current-voltage characteristics of p+n+ In0.53Ga0.47As tunnel junctions

Heavily-doped In_0.53Ga_0.47As tunnel junctions is prepared using molecular beam epitaxy (MBE). Secondary ion mass spectroscopy (SIMS) is used to measure the dopant profiles, these profiles are used to simulate the expected energy band diagrams, and current-voltage characteristics (I-V) are used to characterize the junctions. Devices were fabricated using a self-aligned process to minimize access resistance. Extraction of series resistance from I-V measurements of fabricated tunnel diodes show that the resistance is primarily due to contact resistance (1-2×10^-6 ¿cm²). The lowest doped junction shows good agreement with the predicted values, however the current does not increase with field as expected. This may indicate that the dopant activation is not efficient at higher densities. Room temperature negative differential region (NDR) is not observed in the tunnel diode with the highest effective dopant density, but measurements at 4.2 K show NDR.