6. INCOME TAXES - Deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Deferred tax assets:
Tax credits	$ 4,819	$ 3,958
Net operating losses	113	104
Stock-based compensation	891	899
Property and equipment	138	268
Other reserves and accruals	776	759
Total deferred tax assets	6,737	5,988
Less valuation allowance	(6,700)	(5,913)
Total deferred tax assets	37	75
Deferred tax liabilities:
Unrecognized gains	(2)
Total deferred tax liabilities	(2)
Net deferred tax assets	35	$ 75
Deferred tax liabilities, undistributed foreign earnings	$ 0