As I have discussed before, some cases or ethics opinions have found that the ethical duty to disclose exculpatory evidence is broader than the duty established by Brady v. Maryland (DC and New York, for example, see here and here). Others have held both duties are the same (Wisconsin, for example).
We can now add the Tennessee Supreme Court's Board of Professional Responsibility to the list of those who think the duty is broader. You can read its ethics opinion on the issue here. You can read a comment on it, here.
If you want to read about how a prosecutor approaches the issue of exculpatory evidence, go here.
UPDATE (8/29/19): The Tennessee Supreme Court has vacated the opinion. See here.