Conductance quantization in etched Si/SiGe quantum point contacts

We fabricated strongly confined Schottky-gated quantum point contacts by etching Si/SiGe heterostructures and observed intriguing conductance quantization in units of approximately 1e(2)/h. Nonlinear conductance measurements were performed depleting the quantum point contacts at fixed mode-energy separation. We report evidence of the formation of a half 1e(2)/h plateau, supporting the speculation that adiabatic transmission occurs through one-dimensional modes with complete removal of valley and spin degeneracies.