In [Boylestad and Nashelsky's *Electronic Devices and Circuit Theory*](https://www.amazon.co.uk/Electronic-Devices-Circuit-Theory-Boylestad/dp/0132622262), the structure of GaAs is shown as follows:  

[![GaAs structure, 1][1]][1]

Arsenic is shown making five covalent bonds to neighbouring gallium atoms.

However, I recently also saw an alternative depiction in [Razeghi's *Fundamentals of Solid State Engineering*](https://www.amazon.com/Fundamentals-Solid-State-Engineering-3rd/dp/0387921672):

[![GaAs structure, 1][2]][2]

Here, arsenic is shown making four covalent bonds to neighbouring gallium.

Which source is correct? Please give appropriate references or experimental proof.

  [1]: https://i.stack.imgur.com/1UFhZ.png
  [2]: https://i.stack.imgur.com/QxV4T.png