For HgCdTe liquid phase epitaxy (LPE), in situ differential thermal analysis apparatus is used to precisely monitor the liquidus temperature of each HgCdTe melt. The neutral body, e.g. a slug of copper enclosed in a silica ampoule, is placed near the LPE reactor in a furnace. During heating or cooling, differential sensing of a pair of thermocouples (in the melt and in the neutral body) will show an accelerated change at transformation points, since at these points the temperature of the melt will be changed by the energy of the physical change, while that of the neutral body remains subject only to passive heat transfer. Thus, the actual liquidus temperature of each melt can be measured with extreme precision, and isothermal or programmed cooling methods of LPE can be precisely and reliably controlled under production conditions.
The present invention relates to a method that reduces the thermal gradient at polymorphic transformation of polysilicon. The cooling rate of conventional furnaces is too rapid in currently used processes. The thermal process includes high stress from polymorphic transformation, which causes the peeling of a polysilicon film and microcracking of the quartz tube and wafer boat. The present invention suggests steps following of reducing cracks of polysilicon in a quartz tube and boat. At first, determines the temperature of polymorphic transformation of said quartz tube and boat. Next, reduces the temperature gradient during heating or cooling of said quartz tube and boat during said temperature of polysilicon transformation. Furthermore, the heating or cooling rates of the furnace is limited to the range of 0.1.degree.-2.degree. C./min to reduce the temperature gradient inside the furnace tube. Therefore, the thermal stress that is caused by the phase transition of the quartz is reduced by the invention and the particles and microcrack issues are also reduced by the invention.
Process for the determination of the turbidity point of a liquid, which consists in progressively cooling the liquid and noting the temperature at which turbidity appears; the temperatures at the center (T.sub.1) and at the periphery (T.sub.2) of the liquid are measured, their graphs as a function of time (.theta.) are plotted and changes in the slope of these graphs are noted, the turbidity point being the temperature (T.sub.1) at the center of the liquid which corresponds to the change in slope on the graph T.sub.2 -.function.'(.theta.).
The calorimeter comprises an external accommodating head (23) with two cavities (26, 27) which are capable of receiving a measurement cell (29), in which the specimen to be examined is inserted, and a reference cell (31); the cells (29, 31) are surrounded by a thermoresistor (229), the variation of the resistance of which is determined by a temperature variation, and a heater (129). The two cavities (26, 27) are closed by covers (35, 37) traversed by tubular stems (47-49) capable of supporting the cells (29, 31) for the insertion, into one of them, of a specimen contained in a tubular container (53), which is immersed in a chamber (29A) in which a fluid having high thermal conductivity is present; said cavities (26, 27) are reached by conduits (41, 43; 45) so as to be subjected to vacuum or to controlled pressure using replaceable gases (air, hydrogen, etc.).
The present invention is an infrared-heated differential thermal analyzing instrument. The instrument uses an actively cooled heat sink, and a heat flow restricting element connecting the heat sink to a differential thermal analysis sensor. An IR heater directs IR radiation onto the lateral surfaces of the heat sink and the heat flow restricting element. These lateral surfaces are polished and coated with a high IR reflectance coating, so that heat absorption is minimized. The IR heater preferably uses either elliptical or parabolic mirrors to focus the IR radiation onto the heat sink and the heat flow restricting element. A second embodiment of the invention uses two heat sinks, and two heat flow restricting elements, with one heat sink and one heat flow restricting element mounted on either side of the differential analysis thermal sensor.
A photodiode for detection of preferably infrared radiation wherein photons are absorbed in one region and detected in another. In one example embodiment, an absorbing P region is abutted with an N region of lower doping such that the depletion region is substantially (preferably completely) confined to the N region. The N region is also chosen with a larger bandgap than the P region, with compositional grading of a region of the N region near the P region. This compositional grading mitigates the barrier between the respective bandgaps. Under reverse bias, the barrier is substantially reduced or disappears, allowing charge carriers to move from the absorbing P region into the N region (and beyond) where they are detected. The N region bandgap is chosen to be large enough that the dark current is limited by thermal generation from the field-free p-type absorbing volume, and also large enough to eliminate tunnel currents in the wide gap region of the diode.
