6. INCOME TAXES - Deferred tax assets and liabilities (Details) - USD ($)	Mar. 31, 2022	Mar. 31, 2021
Deferred tax assets:
Tax credits	$ 7,861,000	$ 6,975,000
Net operating losses	5,207,000	2,980,000
Stock-based compensation	1,171,000	1,180,000
Property and equipment	771,000	807,000
Other reserves and accruals	1,384,000	1,267,000
Total deferred tax assets	16,394,000	13,209,000
Valuation allowance	(16,183,000)	(13,017,000)
Total deferred tax assets	211,000	192,000
Deferred tax liabilities:
Leased assets	(244,000)	(186,000)
Unrecognized gains		(15,000)
Unrecognized gains	22,000
Total deferred tax liabilities	(222,000)	(201,000)
Net deferred tax liability	11,000	$ 9,000
Deferred tax liabilities, undistributed foreign earnings	$ 0