Infra red detectors and methods of manufacturing infra red detectors using MOVPE
View Patent ↗A method of forming infra red detector arrays is described, starting with the manufacture of a wafer. The wafer is formed from a GaAs or GaAs/Si substrate having CMT deposited thereon by MOVPE. The CMT deposited comprises a number of layers of differing composition, the composition being controlled during the MOVPE process and being dependent on the thickness of the layer deposited. Other layers are positioned between the active CMT layers and the substrate. A CdTe buffer layer aids the deposition of the CMT on the substrate and an etch stop layer is also provided. Once the wafer is formed, the buffer layer, the etch stop layer and all intervening layers are etched away leaving a wafer suitable for further processing into an infra red detector.
1. A method of producing an infrared detector comprising:
a) forming a cadmium mercury telluride (CMT) wafer that includes active device layers having an absorber layer that is sandwiched between two layers with higher x(Cd) that will passivate diode pn junction where it reaches the surface of a CMT heterostructure;
b) forming a spacer layer, a buffer layer, and an etch stop layer between the active device layers and a substrate;
c) forming arrays of cone-shaped pseudo-loophole diodes in the CMT wafer by ion beam milling through a photo-resist mask, and depositing metal through the same photo-resist mask to form contacts;
d) dicing the CMT wafer into individual arrays, wherein the active layers of the CMT wafer are of uniform thickness;
e) bump-bonding said arrays to read out integrated circuits (ROICS); and
f) removing remaining material of the substrate from the arrays by etching.
2. The method for producing an infrared detector according to claim 1 , in which after bump-bonding a gap between a CMT array and a ROIC is filled with glue.