This dissertation investigates the use of semimetal-semiconductor junctions to enhance a variety of applications while focusing primarily on low-noise Schottky detectors and low-resistance tunnel junctions.

ErAs is the semimetal used in this dissertation. ErAs has the rock salt structure and a lattice constant of 5.74 Å which is conveniently between that of GaAs and InP. The similar lattice type and size makes it possible to integrate single crystal ErAs particles within or grow single crystal films up to ∼75 Å thick on GaAs or In_0.53Ga_0.47As. For both particles and films grown on (100) interfaces the two crystal structures share an arsenic sublattice.

Schottky diodes of ErAs on In_0.53Ga_0.47As or InGaAlAs have a well defined Schottky barrier height that follows conduction band offsets between In_0.53Ga_0.47As and In_0.52Al _0.48As, has a good responsivity, and a very low 1/f noise level. These properties make them a successful candidate for high-frequency radiation detectors. Noise equivalent power of antenna coupled ErAs diode detectors has been measured at 1×10^-12 [W/Hz^1/2] at 104 GHz and 4×10 ^-12 [W/Hz^1/2] at 639 GHz, making them some of the most sensitive passive room-temperature detectors operating at these frequencies.

By incorporating flat, pancake-like ErAs particles into tunnel junctions, the conductivity can be increased by ∼five orders of magnitude, which is useful for creating low-loss tunnel junctions for photovoltaic solar cells.

Finally, a new island-stacking growth technique was developed that allows the Schottky barrier height between ErAs and GaAs to be changed by accessing non-{100} interfaces. This is demonstrated with Schottky diodes where the barrier height can be changed between a particular metal semiconductor interface, and also incorporated into tunnel junctions to increase the conductivity ∼five times higher than flat ErAs islands alone.