ORGANIZATION AND DESCRIPTION OF BUSINESS - Narrative (Details) $ in Thousands		1 Months Ended	3 Months Ended		12 Months Ended
	Feb. 11, 2020 USD ($)	May 12, 2021 USD ($)	Mar. 31, 2021 USD ($) segment patent	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Subsidiary, Sale of Stock [Line Items]
Number of operating segments | segment			1
Accumulated deficit			$ 159,729		$ 150,906
Net loss			(8,823)	$ (8,005)
Cash used			(7,800)
Cash and cash equivalents			21,589		24,968
Sale of common stock net of offering costs	$ 28,800		4,094	$ 26,460
At-The-Market Equity Offering
Subsidiary, Sale of Stock [Line Items]
Sale of common stock net of offering costs			$ 4,200		$ 11,400
Subsequent Event | At-The-Market Equity Offering
Subsidiary, Sale of Stock [Line Items]
Sale of common stock net of offering costs		$ 500
IP Portfolio
Subsidiary, Sale of Stock [Line Items]
Number of developed technology patents | patent			320
IP Portfolio, XBAR Technology
Subsidiary, Sale of Stock [Line Items]
Number of developed technology patents | patent			165