Abstract: The disclosed systems and methods relate generally to techniques for determining the expected cost of a loan repayment program over a given period of time. The systems and methods can calculate a fee for the loan repayment program based on repayment difficulty/non-repayment patterns, underlying economic conditions, and extrapolated enrollment and graduation data.

Abstract: An optically switchable device (1) has a heterostructure (2) defining a first potential well (3) separated by a barrier layer (4) from a second potential well (5) which provides an electron energy level (e.sub.5) which is lower in electron energy than the lowest electron energy level (e.sub.3) of the first potential well (3). The barrier layer (4) provides an intermediate electron energy level (e.sub.4) and is sufficiently thick to inhibit tunnelling of holes from the first (3) to the second (5) potential well. The barrier layer (4) thus confines holes of electron-hole pairs generated in the first potential well (3) by an incident optical beam to the first potential well (3) while facilitating transfer of the electrons from the first potential well (3) to the second potential well (5) via the intermediate electron energy level (e.sub.4) provided by the barrier layer (4).

Abstract: A semiconductor body (1) is provided by growing epitaxial layers of semiconductor material on a substrate placed within a processing chamber and forming a mesa structure (3) on an upper epitaxial layer (2). The mesa structure (3) is formed by epitaxially growing, with the semiconductor body (1) still within the processing chamber, a first layer (4) of a semiconductor material different from that of the upper layer (2) on the upper layer (2) and the opening a window (5) in the first layer (4) to expose an area (2a) of the upper layer (2). A further layer (6) of a semiconductor material different from that of the first layer (4) is then epitaxially grown on the first layer (4) and on the said area (2a) of the upper layer. The first layer (4) is then selectively etched so as to remove the first layer (4) and the part of the further layer (6) carried by the first layer ( 14) leaving the remainder (60a, 60b) of the further layer (6) in the window (5) to form the mesa structure (3).

Abstract: Current flow through the base region of a hot charge-carrier transistor is by hot majority charge-carriers (i.e. hot electrons for a hot electron transistor) which are injected into the base region at an emitter-base barrier region. This barrier region is doped with an impurity of the opposite conductivity type (p type for a hot electron transistor) and is sufficiently thin as to form a bulk unipolar diode with an adjacent part of the base region. In accordance with the invention, the emitter-base barrier region is of different bandgap semiconductor material (for example, gallium aluminum arsenide) compared with that (for example, gallium arsenide) of the base region so as to form a heterojunction. The barrier height of this barrier region is determined in part by the opposite-type doping and in part by the heterojunction and can be made large so as to increase the energy of the injected charge-carriers and hence the collector efficiency of the transistor.

Abstract: A method of growing an n-type GaAs layer on a substrate by a molecular beam epitaxy process, the dopant consisting of S, Se or Te. The layer is prepared by directing molecular beams of gallium, arsenic and PbX, where X is S, Se or Te, onto a heated substrate. It has not proved practicable to grow an n-type GaAs layer by molecular beam epitaxy using S, Se or Te as dopant in the form of a molecular beam consisting of elemental S, Se or Te.

Abstract: The invention provides a thermal camera tube having a reticulated pyroelectric target, that is to say a target having a plurality of separate pyroelectric elements arranged in rows and columns and separated by channels. Each of the separate elements has the shape of a cube the vertical sides of which are inclined so that, except for those in one outer column and one outer row, on two of its sides the top of each element overhangs the base of an adjacent element in the same row and the base on an adjacent element in the same column so that the overhanging surface of the element is exposed to radiation in the region of channels separating it from the aforementioned adjacent elements.