9. STOCK- BASED COMPENSATION (Tables)

12 Months Ended

Mar. 31, 2018

STOCK- BASED COMPENSATION

Summary of stock option activities

			Weighted
		Number of Shares	Average	Weighted
	Shares	Underlying	Remaining	Average
	Available for	Options	Contractual	Exercise		Intrinsic
	Grant	Outstanding	Life (Years)	Price		Value
Balance at March 31, 2015	6,213,943	6,774,151		$	5.16
Options reserved	1,156,419	—			—
Granted	(969,913)	969,913		$	4.42
Exercised	—	(76,745)		$	4.19	$	46,977
Forfeited	31,614	(41,614)		$	4.82
Balance at March 31, 2016	6,432,063	7,625,705		$	5.08
Options reserved	1,085,818	—			—
Terminated plan	(705,699)	—			—
Granted	(1,362,798)	1,362,798		$	5.14
Exercised	—	(391,039)		$	3.96	$	855,160
Forfeited	14,801	(974,634)		$	5.53
Balance at March 31, 2017	5,464,185	7,622,830		$	5.09
Granted	(1,029,684)	1,029,684		$	7.28
Exercised	—	(678,897)		$	4.22	$	2,460,812
Forfeited	9,800	(99,350)		$	5.06
Balance at March 31, 2018	4,444,301	7,874,267	5.59	$	5.45
Options vested and exercisable		4,813,309	3.87	$	5.25	$	10,598,173
Options vested and expected to vest		7,809,354	5.56	$	5.44	$	15,656,510

Schedule of options outstanding by exercise price

				Number of	Options Outstanding			Options Exercisable
				Shares	Weighted		Weighted Average		Weighted
				Underlying	Average		Remaining	Number	Average
				Options	Exercise		Contractual	Vested and	Exercise
Exercise Price				Outstanding	Price		Life (Years)	Exercisable	Price
$	2.43	-	3.60	903,633	$	3.37	4.26	689,079	$	3.34
$	3.75	-	4.17	905,706	$	4.03	1.95	905,706	$	4.03
$	4.30	-	4.98	1,180,166	$	4.83	5.64	692,684	$	4.76
$	4.99	-	5.23	1,158,816	$	5.10	7.45	177,739	$	5.12
$	5.28	-	6.00	975,486	$	5.64	5.38	830,592	$	5.70
$	6.16	-	6.54	849,678	$	6.35	5.30	622,445	$	6.41
$	6.61	-	6.86	843,896	$	6.80	6.23	604,005	$	6.78
$	7.00	-	7.40	817,496	$	7.22	7.92	182,509	$	7.05
$	8.09			130,810	$	8.09	9.83	-	$	-
$	9.20			108,580	$	9.20	2.84	108,580	$	9.20
				7,874,267	$	5.45	5.59	4,813,339	$	5.25

Summary of stock-based compensation expense by line item

	Year Ended March 31,
	2018		2017		2016
	(In thousands)
Cost of revenues	$	259	$	282	$	320
Research and development		1,141		980		858
Selling, general and administrative		670		615		672
Total	$	2,070	$	1,877	$	1,850

Schedule of weighted average assumptions

	Year Ended March 31,
	2018				2017				2016
	(In thousands)
Stock Option Plans:
Risk-free interest rate	1.84	-	2.49	%	1.12	-	1.95	%	1.41	-	1.57	%
Expected life (in years)			5.00				5.00				5.00
Volatility	35.5	-	36.5	%	33.3	-	35.4	%	36.3	-	38.0	%
Dividend yield			—	%			—	%			—	%
Employee Stock Purchase Plan:
Risk-free interest rate	0.38	-	0.45	%	0.38	-	0.45	%	0.09	-	0.15	%
Expected life (in years)			0.50				0.50				0.50
Volatility	30.8	-	39.6	%	30.8	-	39.6	%	26.3	-	27.9	%
Dividend yield			—	%			—	%			—	%