9. STOCK- BASED COMPENSATION - Stock-based compensation expense (Details) - USD ($)	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Stock-based compensation expense by line item
Stock-based compensation expense	$ 1,850,000	$ 2,077,000	$ 2,228,000
Other information
Income tax benefit recognized from allocation of share-based compensation expense	0	0
Windfall tax benefits recognized			33,000
Unrecognized compensation costs	$ 2,900,000
Weighted average period of recognition of unrecognized compensation costs	2 years 1 month 17 days
Cost of revenues
Stock-based compensation expense by line item
Stock-based compensation expense	$ 320,000	401,000	386,000
Research and development
Stock-based compensation expense by line item
Stock-based compensation expense	858,000	941,000	970,000
Selling, general and administrative
Stock-based compensation expense by line item
Stock-based compensation expense	672,000	735,000	872,000
2007 Employee Stock Purchase Plan
Stock-based compensation expense by line item
Stock-based compensation expense	$ 136,000	$ 153,000	$ 152,000