Highly strained Esaki tunnel diodes on InP substrate with type-III band alignment

The first of a kind InP-based Esaki tunnel diodes with type-III (broken gap) band alignment are presented. This type is expected to have the highest tunneling current densities at equal doping concentration and structure geometry, compared to homo-, type-I or type-II junctions. The broken gap alignment is achieved by highly strained n-Ga_0.2In_0.8As/p-GaAs_0.2Sb_0.8 junction layers. Samples were fabricated by molecular beam epitaxy, the junction doping was varied between 2 ×10¹⁸ cm^-3 and 2 ×10¹⁹ cm^-3. Peak current densities up to 34.0 kA cm^-2, for a doping of 2 ×10¹⁹ cm^-3, are reached. The peak tunneling current shows a low dependence on the doping level for the type-III aligned junction layers. For example, highly strained diodes with a doping concentration of 2 ×10¹⁸ cm^-3 can reach peak tunnel current densities of 3.6 A cm^-2, whereas, with the lattice-matched junction, one order of magnitude higher doping is required.