Abstract: A spin coherent, single photon detector has a body of semiconductor material with a quantum well region formed in barrier material in the body. The body has a first electrode forming an isolation electrode for defining, when negatively energized, an extent of the quantum well in the body and a second electrode positioned above a location where an electrostatic quantum dot is defined in said quantum well when positively energized. The quantum well occurs in three layers of material: a central quantum well layer and two outer quantum well layers, the two outer quantum well layers having a relatively low conduction band minimum and the barrier having a relatively high conduction band minimum while the central quantum well layer having a conduction band minimum between the relatively high and relatively low conduction band minimums.

Abstract: The invention provides an effective means and apparatus for allowing higher operational frequencies in heterojunction bipolar transistors by trapping silicon interstitial atoms and thereby preventing transient enhanced diffusion of boron the transistor. The invention provides for selective placement of a carbon layer in the emitter region of a heterojunction bipolar transistor. Such a layer is capable of effectively eliminating transient enhanced boron diffusion without the undesirable performance consequences.