6. INCOME TAXES - Deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Mar. 31, 2019
Deferred tax assets:
Tax credits	$ 5,512	$ 4,819
Net operating losses	1,245	113
Stock-based compensation	950	891
Property and equipment	731	138
Other reserves and accruals	976	776
Total deferred tax assets	9,414	6,737
Valuation allowance	(9,389)	(6,700)
Total deferred tax assets	25	37
Deferred tax liabilities:
Unrecognized gains	(32)	(2)
Total deferred tax liabilities	(32)	(2)
Net deferred tax assets		$ 35
Net deferred tax liability	7
Deferred tax liabilities, undistributed foreign earnings	$ 0