Method of cadmium molecular beam based anneals for manufacture of HgCdTe photodiode arrays
OwnerChang-Feng Waninventor
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Abstract
In the preferred embodiment of the present invention, narrow bandgap II-VI compound semiconductor HgxCd1-xTe (0.1≦x≦0.5) (HgCdTe) wafers are annealed under Cd supersaturated conditions by exposing the HgCdTe planar or mesa surfaces to a Cd molecular beam in a vacuum deposition system before, during, and/or after anneals performed during individual photodiode fabrication process steps or HgCdTe epitaxial growth steps for eliminating or neutralizing the bulk or interfacial defects.
Claims21
A method for thermal treating a HgCdTe layer on a substrate in accordance to the following process steps in this order:
- (1) placing said HgCdTe layer in a vacuum deposition system equipped with a Cd molecular beam source,
- (2) heating said HgCdTe layer to an elevated temperature for anneal or thermal treatment,
- (3) Impinging the front surface of said HgCdTe layer with said Cd molecular beam with a flux exceeding that for Cd saturation of said front surface for at least 15 minutes during said anneal,
- (4) cooling said HgCdTe layer to a certain ending temperature,
- (5) turning off said Cd molecular beam, and
- (6) cooling said HgCdTe layer to room temperature.
A method for removing copper impurity from a CdTe or CdZnTe substrate comprising the following process steps in this order:
- (1) Depositing a Te-rich CdTe layer on the backside of said substrates,
- (2) placing said substrates in a vacuum deposition system equipped with a Cd molecular beam source,
- (3) heating and annealing said substrate at elevated temperatures,
- (4) Impinging the front surface of said HgCdTe layer with said Cd molecular beam having Cd flux intensity substantially exceeds that for Cd saturation for at least 15 minutes during said annealing,
- (5) cooling said substrate to room temperature,
- (6) removing said Te-rich CdTe layer from said CdZnTe by lapping or etching.
The x-value profile of HgCdTe layer from its bare surface or its interface with an insulator layer near a p-n junction formed in said HgCdTe layer assumes that of one-sided diffusion wherein the x-value at said surface or said interface is 1.0 and decreases monotonically and continuously with depth to the starting or bulk x-value of said HgCdTe layer without any inflection point.
Dependencies are inferred from the claim text.